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	$55.52	6.567%	$59.166	$59.17	$59.15	$59.20
Purchase #2	$98.50	8.520%	$106.8922	$106.89	$106.90	$106.90
Purchase #3	$192.85	8.535%	$209.3097	$209.31	$209.30	$209.30
Purchase #4	$31.93	8.211%	$34.5518	$34.55	$34.55	$34.60
Purchase #5	$42.70	13.565%	$48.4923	$48.49	$48.50	$48.50
Purchase #6	$242.85	5.674%	$256.6293	$256.63	$256.65	$256.60
Purchase #7	$94.83	5.425%	$99.9745	$99.97	$99.95	$100.00
7 purchase totals =	$759.18		$815.0158	$815.01	$815.00	$815.10