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	$165.79	11.821%	$185.388	$185.39	$185.40	$185.40
Purchase #2	$50.50	9.870%	$55.4844	$55.48	$55.50	$55.50
Purchase #3	$147.37	7.799%	$158.8634	$158.86	$158.85	$158.90
Purchase #4	$65.90	11.124%	$73.2307	$73.23	$73.25	$73.20
Purchase #5	$242.35	13.488%	$275.0382	$275.04	$275.05	$275.00
Purchase #6	$55.88	5.222%	$58.7981	$58.80	$58.80	$58.80
Purchase #7	$212.86	8.302%	$230.5316	$230.53	$230.55	$230.50
7 purchase totals =	$940.65		$1,037.3344	$1,037.33	$1,037.40	$1,037.30