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	$57.40	7.175%	$61.5185	$61.52	$61.50	$61.50
Purchase #2	$36.66	9.464%	$40.1295	$40.13	$40.15	$40.10
Purchase #3	$211.64	5.689%	$223.6802	$223.68	$223.70	$223.70
Purchase #4	$54.96	8.518%	$59.6415	$59.64	$59.65	$59.60
Purchase #5	$39.47	10.795%	$43.7308	$43.73	$43.75	$43.70
Purchase #6	$76.61	11.599%	$85.496	$85.50	$85.50	$85.50
Purchase #7	$71.55	7.320%	$76.7875	$76.79	$76.80	$76.80
7 purchase totals =	$548.29		$590.9840	$590.99	$591.05	$590.90