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	$196.52	7.433%	$211.1273	$211.13	$211.15	$211.10
Purchase #2	$67.79	3.288%	$70.0189	$70.02	$70.00	$70.00
Purchase #3	$6.84	4.864%	$7.1727	$7.17	$7.15	$7.20
Purchase #4	$148.33	11.738%	$165.741	$165.74	$165.75	$165.70
Purchase #5	$76.38	9.700%	$83.7889	$83.79	$83.80	$83.80
Purchase #6	$118.68	8.632%	$128.9245	$128.92	$128.90	$128.90
Purchase #7	$108.70	13.231%	$123.0821	$123.08	$123.10	$123.10
7 purchase totals =	$723.24		$789.8554	$789.85	$789.85	$789.80