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	$169.66	9.531%	$185.8303	$185.83	$185.85	$185.80
Purchase #2	$39.71	5.657%	$41.9564	$41.96	$41.95	$42.00
Purchase #3	$150.63	13.796%	$171.4109	$171.41	$171.40	$171.40
Purchase #4	$18.88	9.761%	$20.7229	$20.72	$20.70	$20.70
Purchase #5	$151.59	12.604%	$170.6964	$170.70	$170.70	$170.70
Purchase #6	$65.49	3.719%	$67.9256	$67.93	$67.95	$67.90
Purchase #7	$71.32	7.382%	$76.5848	$76.58	$76.60	$76.60
7 purchase totals =	$667.28		$735.1273	$735.13	$735.15	$735.10