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	$168.82	7.127%	$180.8518	$180.85	$180.85	$180.90
Purchase #2	$35.49	13.700%	$40.3521	$40.35	$40.35	$40.40
Purchase #3	$27.30	11.319%	$30.3901	$30.39	$30.40	$30.40
Purchase #4	$143.59	5.594%	$151.6224	$151.62	$151.60	$151.60
Purchase #5	$9.60	10.830%	$10.6397	$10.64	$10.65	$10.60
Purchase #6	$180.73	4.787%	$189.3815	$189.38	$189.40	$189.40
Purchase #7	$169.41	10.345%	$186.9355	$186.94	$186.95	$186.90
7 purchase totals =	$734.94		$790.1731	$790.17	$790.20	$790.20