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	$62.76	8.230%	$67.9251	$67.93	$67.95	$67.90
Purchase #2	$123.36	5.581%	$130.2447	$130.24	$130.25	$130.20
Purchase #3	$129.59	7.223%	$138.9503	$138.95	$138.95	$139.00
Purchase #4	$102.86	8.683%	$111.7913	$111.79	$111.80	$111.80
Purchase #5	$92.90	13.374%	$105.3244	$105.32	$105.30	$105.30
Purchase #6	$55.30	11.286%	$61.5412	$61.54	$61.55	$61.50
Purchase #7	$233.35	7.596%	$251.0753	$251.08	$251.10	$251.10
7 purchase totals =	$800.12		$866.8523	$866.85	$866.90	$866.80