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	$127.76	9.166%	$139.4705	$139.47	$139.45	$139.50
Purchase #2	$227.54	10.391%	$251.1837	$251.18	$251.20	$251.20
Purchase #3	$45.39	6.640%	$48.4039	$48.40	$48.40	$48.40
Purchase #4	$149.28	4.188%	$155.5318	$155.53	$155.55	$155.50
Purchase #5	$88.63	10.695%	$98.109	$98.11	$98.10	$98.10
Purchase #6	$127.33	11.392%	$141.8354	$141.84	$141.85	$141.80
Purchase #7	$210.62	8.760%	$229.0703	$229.07	$229.05	$229.10
7 purchase totals =	$976.55		$1,063.6046	$1,063.60	$1,063.60	$1,063.60