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	$205.70	13.678%	$233.8356	$233.84	$233.85	$233.80
Purchase #2	$103.91	6.356%	$110.5145	$110.51	$110.50	$110.50
Purchase #3	$87.43	4.269%	$91.1624	$91.16	$91.15	$91.20
Purchase #4	$110.96	11.112%	$123.2899	$123.29	$123.30	$123.30
Purchase #5	$48.30	13.590%	$54.864	$54.86	$54.85	$54.90
Purchase #6	$87.79	10.213%	$96.756	$96.76	$96.75	$96.80
Purchase #7	$131.67	6.821%	$140.6512	$140.65	$140.65	$140.70
7 purchase totals =	$775.76		$851.0736	$851.07	$851.05	$851.20