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	$68.63	8.352%	$74.362	$74.36	$74.35	$74.40
Purchase #2	$18.47	5.784%	$19.5383	$19.54	$19.55	$19.50
Purchase #3	$107.33	3.380%	$110.9578	$110.96	$110.95	$111.00
Purchase #4	$218.32	6.820%	$233.2094	$233.21	$233.20	$233.20
Purchase #5	$155.93	8.313%	$168.8925	$168.89	$168.90	$168.90
Purchase #6	$154.65	10.842%	$171.4172	$171.42	$171.40	$171.40
Purchase #7	$223.45	7.476%	$240.1551	$240.16	$240.15	$240.20
7 purchase totals =	$946.78		$1,018.5323	$1,018.54	$1,018.50	$1,018.60