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	$174.67	8.532%	$189.5728	$189.57	$189.55	$189.60
Purchase #2	$232.28	7.103%	$248.7788	$248.78	$248.80	$248.80
Purchase #3	$28.28	13.576%	$32.1193	$32.12	$32.10	$32.10
Purchase #4	$214.80	8.753%	$233.6014	$233.60	$233.60	$233.60
Purchase #5	$68.94	5.450%	$72.6972	$72.70	$72.70	$72.70
Purchase #6	$133.77	13.547%	$151.8918	$151.89	$151.90	$151.90
Purchase #7	$171.56	6.808%	$183.2398	$183.24	$183.25	$183.20
7 purchase totals =	$1,024.30		$1,111.9011	$1,111.90	$1,111.90	$1,111.90