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	$186.25	7.814%	$200.8036	$200.80	$200.80	$200.80
Purchase #2	$78.38	13.644%	$89.0742	$89.07	$89.05	$89.10
Purchase #3	$185.91	3.660%	$192.7143	$192.71	$192.70	$192.70
Purchase #4	$190.35	5.362%	$200.5566	$200.56	$200.55	$200.60
Purchase #5	$209.58	5.408%	$220.9141	$220.91	$220.90	$220.90
Purchase #6	$6.61	12.739%	$7.452	$7.45	$7.45	$7.50
Purchase #7	$193.72	11.863%	$216.701	$216.70	$216.70	$216.70
7 purchase totals =	$1,050.80		$1,128.2158	$1,128.20	$1,128.15	$1,128.30