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	$167.71	10.508%	$185.333	$185.33	$185.35	$185.30
Purchase #2	$211.36	9.391%	$231.2088	$231.21	$231.20	$231.20
Purchase #3	$108.94	8.330%	$118.0147	$118.01	$118.00	$118.00
Purchase #4	$221.96	5.827%	$234.8936	$234.89	$234.90	$234.90
Purchase #5	$198.40	11.726%	$221.6644	$221.66	$221.65	$221.70
Purchase #6	$118.53	12.635%	$133.5063	$133.51	$133.50	$133.50
Purchase #7	$65.61	9.256%	$71.6829	$71.68	$71.70	$71.70
7 purchase totals =	$1,092.51		$1,196.3037	$1,196.29	$1,196.30	$1,196.30