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	$158.26	13.350%	$179.3877	$179.39	$179.40	$179.40
Purchase #2	$71.55	7.853%	$77.1688	$77.17	$77.15	$77.20
Purchase #3	$47.53	10.358%	$52.4532	$52.45	$52.45	$52.50
Purchase #4	$211.80	6.387%	$225.3277	$225.33	$225.35	$225.30
Purchase #5	$243.80	6.820%	$260.4272	$260.43	$260.45	$260.40
Purchase #6	$129.84	5.809%	$137.3824	$137.38	$137.40	$137.40
Purchase #7	$213.51	9.546%	$233.8917	$233.89	$233.90	$233.90
7 purchase totals =	$1,076.29		$1,166.0387	$1,166.04	$1,166.10	$1,166.10