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	$140.54	7.245%	$150.7221	$150.72	$150.70	$150.70
Purchase #2	$130.40	9.217%	$142.419	$142.42	$142.40	$142.40
Purchase #3	$88.71	12.501%	$99.7996	$99.80	$99.80	$99.80
Purchase #4	$185.63	3.508%	$192.1419	$192.14	$192.15	$192.10
Purchase #5	$72.60	5.280%	$76.4333	$76.43	$76.45	$76.40
Purchase #6	$90.28	3.723%	$93.6411	$93.64	$93.65	$93.60
Purchase #7	$46.31	9.368%	$50.6483	$50.65	$50.65	$50.60
7 purchase totals =	$754.47		$805.8053	$805.80	$805.80	$805.60