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	$146.49	6.145%	$155.4918	$155.49	$155.50	$155.50
Purchase #2	$158.74	10.173%	$174.8886	$174.89	$174.90	$174.90
Purchase #3	$48.98	7.216%	$52.5144	$52.51	$52.50	$52.50
Purchase #4	$221.65	11.645%	$247.4611	$247.46	$247.45	$247.50
Purchase #5	$46.78	8.311%	$50.6679	$50.67	$50.65	$50.70
Purchase #6	$192.50	6.794%	$205.5785	$205.58	$205.60	$205.60
Purchase #7	$166.40	5.471%	$175.5037	$175.50	$175.50	$175.50
7 purchase totals =	$981.54		$1,062.1060	$1,062.10	$1,062.10	$1,062.20