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	$204.57	12.512%	$230.1658	$230.17	$230.15	$230.20
Purchase #2	$103.56	7.805%	$111.6429	$111.64	$111.65	$111.60
Purchase #3	$182.30	7.640%	$196.2277	$196.23	$196.25	$196.20
Purchase #4	$94.82	3.700%	$98.3283	$98.33	$98.35	$98.30
Purchase #5	$75.35	8.744%	$81.9386	$81.94	$81.95	$81.90
Purchase #6	$179.98	9.114%	$196.3834	$196.38	$196.40	$196.40
Purchase #7	$110.87	10.828%	$122.875	$122.88	$122.90	$122.90
7 purchase totals =	$951.45		$1,037.5617	$1,037.57	$1,037.65	$1,037.50