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	$173.40	5.364%	$182.7012	$182.70	$182.70	$182.70
Purchase #2	$53.32	12.217%	$59.8341	$59.83	$59.85	$59.80
Purchase #3	$245.98	12.250%	$276.1126	$276.11	$276.10	$276.10
Purchase #4	$137.88	12.678%	$155.3604	$155.36	$155.35	$155.40
Purchase #5	$174.78	12.343%	$196.3531	$196.35	$196.35	$196.40
Purchase #6	$197.27	13.344%	$223.5937	$223.59	$223.60	$223.60
Purchase #7	$26.80	13.847%	$30.511	$30.51	$30.50	$30.50
7 purchase totals =	$1,009.43		$1,124.4661	$1,124.45	$1,124.45	$1,124.50