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	$156.83	9.583%	$171.859	$171.86	$171.85	$171.90
Purchase #2	$218.46	13.686%	$248.3584	$248.36	$248.35	$248.40
Purchase #3	$99.98	5.148%	$105.127	$105.13	$105.15	$105.10
Purchase #4	$218.62	4.272%	$227.9594	$227.96	$227.95	$228.00
Purchase #5	$37.30	10.798%	$41.3277	$41.33	$41.35	$41.30
Purchase #6	$59.44	9.412%	$65.0345	$65.03	$65.05	$65.00
Purchase #7	$156.60	11.234%	$174.1924	$174.19	$174.20	$174.20
7 purchase totals =	$947.23		$1,033.8584	$1,033.86	$1,033.90	$1,033.90