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	$41.59	12.439%	$46.7634	$46.76	$46.75	$46.80
Purchase #2	$250.67	11.502%	$279.5021	$279.50	$279.50	$279.50
Purchase #3	$53.97	13.305%	$61.1507	$61.15	$61.15	$61.20
Purchase #4	$123.95	5.832%	$131.1788	$131.18	$131.20	$131.20
Purchase #5	$50.96	6.262%	$54.1511	$54.15	$54.15	$54.20
Purchase #6	$214.65	12.822%	$242.1724	$242.17	$242.15	$242.20
Purchase #7	$241.56	9.751%	$265.1145	$265.11	$265.10	$265.10
7 purchase totals =	$977.35		$1,080.0330	$1,080.02	$1,080.00	$1,080.20