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	$172.38	13.750%	$196.0823	$196.08	$196.10	$196.10
Purchase #2	$91.27	3.162%	$94.156	$94.16	$94.15	$94.20
Purchase #3	$97.54	8.272%	$105.6085	$105.61	$105.60	$105.60
Purchase #4	$85.96	6.430%	$91.4872	$91.49	$91.50	$91.50
Purchase #5	$22.73	11.257%	$25.2887	$25.29	$25.30	$25.30
Purchase #6	$99.48	9.134%	$108.5665	$108.57	$108.55	$108.60
Purchase #7	$5.39	12.281%	$6.0519	$6.05	$6.05	$6.10
7 purchase totals =	$574.75		$627.2411	$627.25	$627.25	$627.40