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	$48.28	3.869%	$50.148	$50.15	$50.15	$50.10
Purchase #2	$221.75	10.438%	$244.8963	$244.90	$244.90	$244.90
Purchase #3	$112.72	5.860%	$119.3254	$119.33	$119.35	$119.30
Purchase #4	$86.72	8.239%	$93.8649	$93.86	$93.85	$93.90
Purchase #5	$94.44	11.716%	$105.5046	$105.50	$105.50	$105.50
Purchase #6	$234.42	6.863%	$250.5082	$250.51	$250.50	$250.50
Purchase #7	$142.76	10.191%	$157.3087	$157.31	$157.30	$157.30
7 purchase totals =	$941.09		$1,021.5561	$1,021.56	$1,021.55	$1,021.50