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	$59.26	11.513%	$66.0826	$66.08	$66.10	$66.10
Purchase #2	$50.55	8.376%	$54.7841	$54.78	$54.80	$54.80
Purchase #3	$38.66	4.476%	$40.3904	$40.39	$40.40	$40.40
Purchase #4	$88.85	9.107%	$96.9416	$96.94	$96.95	$96.90
Purchase #5	$143.34	9.316%	$156.6936	$156.69	$156.70	$156.70
Purchase #6	$67.35	5.516%	$71.065	$71.07	$71.05	$71.10
Purchase #7	$195.76	11.305%	$217.8907	$217.89	$217.90	$217.90
7 purchase totals =	$643.77		$703.8480	$703.84	$703.90	$703.90