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	$241.46	3.648%	$250.2685	$250.27	$250.25	$250.30
Purchase #2	$33.33	11.806%	$37.2649	$37.26	$37.25	$37.30
Purchase #3	$210.49	4.387%	$219.7242	$219.72	$219.70	$219.70
Purchase #4	$6.67	7.153%	$7.1471	$7.15	$7.15	$7.10
Purchase #5	$124.86	13.481%	$141.6924	$141.69	$141.70	$141.70
Purchase #6	$95.64	5.744%	$101.1336	$101.13	$101.15	$101.10
Purchase #7	$114.45	3.730%	$118.719	$118.72	$118.70	$118.70
7 purchase totals =	$826.90		$875.9497	$875.94	$875.90	$875.90