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	$227.51	12.564%	$256.0944	$256.09	$256.10	$256.10
Purchase #2	$165.77	3.484%	$171.5454	$171.55	$171.55	$171.50
Purchase #3	$142.76	9.180%	$155.8654	$155.87	$155.85	$155.90
Purchase #4	$28.41	3.773%	$29.4819	$29.48	$29.50	$29.50
Purchase #5	$160.38	8.681%	$174.3026	$174.30	$174.30	$174.30
Purchase #6	$49.56	5.315%	$52.1941	$52.19	$52.20	$52.20
Purchase #7	$211.55	10.358%	$233.4623	$233.46	$233.45	$233.50
7 purchase totals =	$985.94		$1,072.9461	$1,072.94	$1,072.95	$1,073.00