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	$114.25	11.811%	$127.7441	$127.74	$127.75	$127.70
Purchase #2	$222.72	9.670%	$244.257	$244.26	$244.25	$244.30
Purchase #3	$36.62	13.182%	$41.4472	$41.45	$41.45	$41.40
Purchase #4	$52.69	12.873%	$59.4728	$59.47	$59.45	$59.50
Purchase #5	$105.40	12.800%	$118.8912	$118.89	$118.90	$118.90
Purchase #6	$145.93	8.617%	$158.5048	$158.50	$158.50	$158.50
Purchase #7	$206.79	8.144%	$223.631	$223.63	$223.65	$223.60
7 purchase totals =	$884.40		$973.9481	$973.94	$973.95	$973.90