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	$169.56	6.712%	$180.9409	$180.94	$180.95	$180.90
Purchase #2	$149.57	11.205%	$166.3293	$166.33	$166.35	$166.30
Purchase #3	$55.82	8.732%	$60.6942	$60.69	$60.70	$60.70
Purchase #4	$104.95	13.110%	$118.7089	$118.71	$118.70	$118.70
Purchase #5	$159.45	3.692%	$165.3369	$165.34	$165.35	$165.30
Purchase #6	$69.48	12.789%	$78.3658	$78.37	$78.35	$78.40
Purchase #7	$90.56	13.313%	$102.6163	$102.62	$102.60	$102.60
7 purchase totals =	$799.39		$872.9923	$873.00	$873.00	$872.90