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	$52.69	9.373%	$57.6286	$57.63	$57.65	$57.60
Purchase #2	$115.91	4.358%	$120.9614	$120.96	$120.95	$121.00
Purchase #3	$198.42	12.637%	$223.4943	$223.49	$223.50	$223.50
Purchase #4	$199.83	4.353%	$208.5286	$208.53	$208.55	$208.50
Purchase #5	$132.95	10.527%	$146.9456	$146.95	$146.95	$146.90
Purchase #6	$195.42	10.782%	$216.4902	$216.49	$216.50	$216.50
Purchase #7	$123.30	6.366%	$131.1493	$131.15	$131.15	$131.10
7 purchase totals =	$1,018.52		$1,105.1980	$1,105.20	$1,105.25	$1,105.10