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	$182.34	6.253%	$193.7417	$193.74	$193.75	$193.70
Purchase #2	$89.60	4.533%	$93.6616	$93.66	$93.65	$93.70
Purchase #3	$190.70	7.731%	$205.443	$205.44	$205.45	$205.40
Purchase #4	$82.82	8.618%	$89.9574	$89.96	$89.95	$90.00
Purchase #5	$51.52	6.590%	$54.9152	$54.92	$54.90	$54.90
Purchase #6	$67.69	4.166%	$70.51	$70.51	$70.50	$70.50
Purchase #7	$69.71	10.360%	$76.932	$76.93	$76.95	$76.90
7 purchase totals =	$734.38		$785.1609	$785.16	$785.15	$785.10