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	$214.72	9.678%	$235.5006	$235.50	$235.50	$235.50
Purchase #2	$119.44	5.355%	$125.836	$125.84	$125.85	$125.80
Purchase #3	$64.89	10.360%	$71.6126	$71.61	$71.60	$71.60
Purchase #4	$52.83	11.325%	$58.813	$58.81	$58.80	$58.80
Purchase #5	$189.89	13.358%	$215.2555	$215.26	$215.25	$215.30
Purchase #6	$212.73	13.790%	$242.0655	$242.07	$242.05	$242.10
Purchase #7	$96.61	9.525%	$105.8121	$105.81	$105.80	$105.80
7 purchase totals =	$951.11		$1,054.8953	$1,054.90	$1,054.85	$1,054.90