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	$26.96	5.434%	$28.425	$28.43	$28.45	$28.40
Purchase #2	$193.46	12.253%	$217.1647	$217.16	$217.15	$217.20
Purchase #3	$33.95	8.165%	$36.722	$36.72	$36.70	$36.70
Purchase #4	$116.31	9.621%	$127.5002	$127.50	$127.50	$127.50
Purchase #5	$91.48	9.715%	$100.3673	$100.37	$100.35	$100.40
Purchase #6	$171.58	6.257%	$182.3158	$182.32	$182.30	$182.30
Purchase #7	$150.70	13.776%	$171.4604	$171.46	$171.45	$171.50
7 purchase totals =	$784.44		$863.9554	$863.96	$863.90	$864.00