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	$175.76	6.761%	$187.6431	$187.64	$187.65	$187.60
Purchase #2	$157.70	4.799%	$165.268	$165.27	$165.25	$165.30
Purchase #3	$86.71	5.693%	$91.6464	$91.65	$91.65	$91.60
Purchase #4	$89.44	13.729%	$101.7192	$101.72	$101.70	$101.70
Purchase #5	$98.41	7.185%	$105.4808	$105.48	$105.50	$105.50
Purchase #6	$161.25	5.180%	$169.6028	$169.60	$169.60	$169.60
Purchase #7	$40.90	3.309%	$42.2534	$42.25	$42.25	$42.30
7 purchase totals =	$810.17		$863.6137	$863.61	$863.60	$863.60