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	$130.64	8.595%	$141.8685	$141.87	$141.85	$141.90
Purchase #2	$166.50	10.199%	$183.4813	$183.48	$183.50	$183.50
Purchase #3	$118.95	5.328%	$125.2877	$125.29	$125.30	$125.30
Purchase #4	$109.54	8.331%	$118.6658	$118.67	$118.65	$118.70
Purchase #5	$200.89	5.104%	$211.1434	$211.14	$211.15	$211.10
Purchase #6	$56.81	10.501%	$62.7756	$62.78	$62.80	$62.80
Purchase #7	$140.89	13.658%	$160.1328	$160.13	$160.15	$160.10
7 purchase totals =	$924.22		$1,003.3551	$1,003.36	$1,003.40	$1,003.40