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	$142.36	8.814%	$154.9076	$154.91	$154.90	$154.90
Purchase #2	$65.35	10.224%	$72.0314	$72.03	$72.05	$72.00
Purchase #3	$151.82	10.325%	$167.4954	$167.50	$167.50	$167.50
Purchase #4	$232.27	10.446%	$256.5329	$256.53	$256.55	$256.50
Purchase #5	$200.30	10.642%	$221.6159	$221.62	$221.60	$221.60
Purchase #6	$84.53	11.203%	$93.9999	$94.00	$94.00	$94.00
Purchase #7	$68.58	4.743%	$71.8327	$71.83	$71.85	$71.80
7 purchase totals =	$945.21		$1,038.4158	$1,038.42	$1,038.45	$1,038.30