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	$188.63	3.874%	$195.9375	$195.94	$195.95	$195.90
Purchase #2	$173.83	8.429%	$188.4821	$188.48	$188.50	$188.50
Purchase #3	$10.61	11.559%	$11.8364	$11.84	$11.85	$11.80
Purchase #4	$190.41	9.715%	$208.9083	$208.91	$208.90	$208.90
Purchase #5	$50.92	6.564%	$54.2624	$54.26	$54.25	$54.30
Purchase #6	$90.34	5.495%	$95.3042	$95.30	$95.30	$95.30
Purchase #7	$230.83	3.425%	$238.7359	$238.74	$238.75	$238.70
7 purchase totals =	$935.57		$993.4668	$993.47	$993.50	$993.40