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	$174.93	13.364%	$198.3076	$198.31	$198.30	$198.30
Purchase #2	$77.44	4.374%	$80.8272	$80.83	$80.85	$80.80
Purchase #3	$200.92	4.794%	$210.5521	$210.55	$210.55	$210.60
Purchase #4	$131.94	11.109%	$146.5972	$146.60	$146.60	$146.60
Purchase #5	$165.74	9.150%	$180.9052	$180.91	$180.90	$180.90
Purchase #6	$216.78	3.211%	$223.7408	$223.74	$223.75	$223.70
Purchase #7	$228.29	5.203%	$240.1679	$240.17	$240.15	$240.20
7 purchase totals =	$1,196.04		$1,281.0980	$1,281.11	$1,281.10	$1,281.10