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	$184.27	13.124%	$208.4536	$208.45	$208.45	$208.50
Purchase #2	$146.57	10.699%	$162.2515	$162.25	$162.25	$162.30
Purchase #3	$206.96	10.787%	$229.2848	$229.28	$229.30	$229.30
Purchase #4	$93.26	6.796%	$99.5979	$99.60	$99.60	$99.60
Purchase #5	$15.88	12.811%	$17.9144	$17.91	$17.90	$17.90
Purchase #6	$17.61	4.561%	$18.4132	$18.41	$18.40	$18.40
Purchase #7	$176.27	7.338%	$189.2047	$189.20	$189.20	$189.20
7 purchase totals =	$840.82		$925.1201	$925.10	$925.10	$925.20