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	$235.89	4.117%	$245.6016	$245.60	$245.60	$245.60
Purchase #2	$146.95	12.609%	$165.4789	$165.48	$165.50	$165.50
Purchase #3	$19.44	13.811%	$22.1249	$22.12	$22.10	$22.10
Purchase #4	$64.71	9.864%	$71.093	$71.09	$71.10	$71.10
Purchase #5	$213.50	4.686%	$223.5046	$223.50	$223.50	$223.50
Purchase #6	$231.79	8.118%	$250.6067	$250.61	$250.60	$250.60
Purchase #7	$163.49	11.470%	$182.2423	$182.24	$182.25	$182.20
7 purchase totals =	$1,075.77		$1,160.6520	$1,160.64	$1,160.65	$1,160.60