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	$72.65	7.717%	$78.2564	$78.26	$78.25	$78.30
Purchase #2	$39.92	8.720%	$43.401	$43.40	$43.40	$43.40
Purchase #3	$41.97	8.483%	$45.5303	$45.53	$45.55	$45.50
Purchase #4	$184.51	8.776%	$200.7026	$200.70	$200.70	$200.70
Purchase #5	$191.61	10.641%	$211.9992	$212.00	$212.00	$212.00
Purchase #6	$67.83	4.837%	$71.1109	$71.11	$71.10	$71.10
Purchase #7	$130.96	4.188%	$136.4446	$136.44	$136.45	$136.40
7 purchase totals =	$729.45		$787.4450	$787.44	$787.45	$787.40