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	$73.75	7.720%	$79.4435	$79.44	$79.45	$79.40
Purchase #2	$156.62	6.683%	$167.0869	$167.09	$167.10	$167.10
Purchase #3	$198.80	10.573%	$219.8191	$219.82	$219.80	$219.80
Purchase #4	$101.98	11.162%	$113.363	$113.36	$113.35	$113.40
Purchase #5	$76.98	11.773%	$86.0429	$86.04	$86.05	$86.00
Purchase #6	$188.39	4.456%	$196.7847	$196.78	$196.80	$196.80
Purchase #7	$171.25	7.618%	$184.2958	$184.30	$184.30	$184.30
7 purchase totals =	$967.77		$1,046.8359	$1,046.83	$1,046.85	$1,046.80