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	$200.98	6.204%	$213.4488	$213.45	$213.45	$213.40
Purchase #2	$36.73	11.384%	$40.9113	$40.91	$40.90	$40.90
Purchase #3	$146.28	8.116%	$158.1521	$158.15	$158.15	$158.20
Purchase #4	$242.91	9.603%	$266.2366	$266.24	$266.25	$266.20
Purchase #5	$217.35	3.330%	$224.5878	$224.59	$224.60	$224.60
Purchase #6	$159.84	3.702%	$165.7573	$165.76	$165.75	$165.80
Purchase #7	$37.52	7.220%	$40.2289	$40.23	$40.25	$40.20
7 purchase totals =	$1,041.61		$1,109.3228	$1,109.33	$1,109.35	$1,109.30