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	$134.61	5.352%	$141.8143	$141.81	$141.80	$141.80
Purchase #2	$208.92	3.335%	$215.8875	$215.89	$215.90	$215.90
Purchase #3	$34.83	8.314%	$37.7258	$37.73	$37.75	$37.70
Purchase #4	$214.68	9.853%	$235.8324	$235.83	$235.85	$235.80
Purchase #5	$86.55	10.508%	$95.6447	$95.64	$95.65	$95.60
Purchase #6	$42.90	3.494%	$44.3989	$44.40	$44.40	$44.40
Purchase #7	$226.59	9.365%	$247.8102	$247.81	$247.80	$247.80
7 purchase totals =	$949.08		$1,019.1138	$1,019.11	$1,019.15	$1,019.00