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	$247.95	5.391%	$261.317	$261.32	$261.30	$261.30
Purchase #2	$169.83	11.152%	$188.7694	$188.77	$188.75	$188.80
Purchase #3	$109.90	12.234%	$123.3452	$123.35	$123.35	$123.30
Purchase #4	$43.37	12.248%	$48.682	$48.68	$48.70	$48.70
Purchase #5	$197.56	13.145%	$223.5293	$223.53	$223.55	$223.50
Purchase #6	$149.89	7.739%	$161.49	$161.49	$161.50	$161.50
Purchase #7	$134.72	7.331%	$144.5963	$144.60	$144.60	$144.60
7 purchase totals =	$1,053.22		$1,151.7292	$1,151.74	$1,151.75	$1,151.70