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	$219.82	10.766%	$243.4858	$243.49	$243.50	$243.50
Purchase #2	$35.38	6.596%	$37.7137	$37.71	$37.70	$37.70
Purchase #3	$248.41	10.760%	$275.1389	$275.14	$275.15	$275.10
Purchase #4	$90.69	6.386%	$96.4815	$96.48	$96.50	$96.50
Purchase #5	$229.39	13.413%	$260.1581	$260.16	$260.15	$260.20
Purchase #6	$232.31	5.778%	$245.7329	$245.73	$245.75	$245.70
Purchase #7	$81.77	10.563%	$90.4074	$90.41	$90.40	$90.40
7 purchase totals =	$1,137.77		$1,249.1183	$1,249.12	$1,249.15	$1,249.10