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	$141.47	10.346%	$156.1065	$156.11	$156.10	$156.10
Purchase #2	$62.97	11.232%	$70.0428	$70.04	$70.05	$70.00
Purchase #3	$168.25	4.354%	$175.5756	$175.58	$175.60	$175.60
Purchase #4	$105.73	6.139%	$112.2208	$112.22	$112.20	$112.20
Purchase #5	$185.30	3.396%	$191.5928	$191.59	$191.60	$191.60
Purchase #6	$133.89	11.118%	$148.7759	$148.78	$148.80	$148.80
Purchase #7	$7.29	4.295%	$7.6031	$7.60	$7.60	$7.60
7 purchase totals =	$804.90		$861.9175	$861.92	$861.95	$861.90