Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$177.48	9.625%	$194.5625	$194.56	$194.55	$194.60
Purchase #2	$129.71	13.287%	$146.9446	$146.94	$146.95	$146.90
Purchase #3	$171.65	8.136%	$185.6154	$185.62	$185.60	$185.60
Purchase #4	$119.65	7.666%	$128.8224	$128.82	$128.80	$128.80
Purchase #5	$98.84	5.205%	$103.9846	$103.98	$104.00	$104.00
Purchase #6	$239.59	9.819%	$263.1153	$263.12	$263.10	$263.10
Purchase #7	$115.89	13.566%	$131.6116	$131.61	$131.60	$131.60
7 purchase totals =	$1,052.81		$1,154.6564	$1,154.65	$1,154.60	$1,154.60