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	$69.87	3.691%	$72.4489	$72.45	$72.45	$72.40
Purchase #2	$216.26	10.793%	$239.6009	$239.60	$239.60	$239.60
Purchase #3	$222.33	12.575%	$250.288	$250.29	$250.30	$250.30
Purchase #4	$196.43	10.722%	$217.4912	$217.49	$217.50	$217.50
Purchase #5	$98.25	10.850%	$108.9101	$108.91	$108.90	$108.90
Purchase #6	$197.54	9.257%	$215.8263	$215.83	$215.85	$215.80
Purchase #7	$73.94	6.392%	$78.6662	$78.67	$78.65	$78.70
7 purchase totals =	$1,074.62		$1,183.2316	$1,183.24	$1,183.25	$1,183.20