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	$14.82	3.178%	$15.291	$15.29	$15.30	$15.30
Purchase #2	$16.80	10.396%	$18.5465	$18.55	$18.55	$18.50
Purchase #3	$128.97	12.287%	$144.8165	$144.82	$144.80	$144.80
Purchase #4	$156.82	9.389%	$171.5438	$171.54	$171.55	$171.50
Purchase #5	$66.89	7.460%	$71.88	$71.88	$71.90	$71.90
Purchase #6	$243.72	3.190%	$251.4947	$251.49	$251.50	$251.50
Purchase #7	$225.98	3.650%	$234.2283	$234.23	$234.25	$234.20
7 purchase totals =	$854.00		$907.8008	$907.80	$907.85	$907.70