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	$118.31	10.573%	$130.8189	$130.82	$130.80	$130.80
Purchase #2	$40.33	12.423%	$45.3402	$45.34	$45.35	$45.30
Purchase #3	$47.72	6.548%	$50.8447	$50.84	$50.85	$50.80
Purchase #4	$181.83	6.776%	$194.1508	$194.15	$194.15	$194.20
Purchase #5	$53.85	3.518%	$55.7444	$55.74	$55.75	$55.70
Purchase #6	$65.94	4.181%	$68.697	$68.70	$68.70	$68.70
Purchase #7	$133.31	4.686%	$139.5569	$139.56	$139.55	$139.60
7 purchase totals =	$641.29		$685.1529	$685.15	$685.15	$685.10