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	$138.34	13.217%	$156.6244	$156.62	$156.60	$156.60
Purchase #2	$216.44	8.394%	$234.608	$234.61	$234.60	$234.60
Purchase #3	$58.79	13.784%	$66.8936	$66.89	$66.90	$66.90
Purchase #4	$66.77	8.645%	$72.5423	$72.54	$72.55	$72.50
Purchase #5	$235.58	7.863%	$254.1037	$254.10	$254.10	$254.10
Purchase #6	$168.75	3.743%	$175.0663	$175.07	$175.05	$175.10
Purchase #7	$48.29	12.626%	$54.3871	$54.39	$54.40	$54.40
7 purchase totals =	$932.96		$1,014.2254	$1,014.22	$1,014.20	$1,014.20