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	$153.52	10.326%	$169.3725	$169.37	$169.35	$169.40
Purchase #2	$62.82	3.290%	$64.8868	$64.89	$64.90	$64.90
Purchase #3	$212.68	13.184%	$240.7197	$240.72	$240.70	$240.70
Purchase #4	$135.96	9.471%	$148.8368	$148.84	$148.85	$148.80
Purchase #5	$227.56	9.363%	$248.8664	$248.87	$248.85	$248.90
Purchase #6	$164.25	13.176%	$185.8916	$185.89	$185.90	$185.90
Purchase #7	$23.65	8.736%	$25.7161	$25.72	$25.70	$25.70
7 purchase totals =	$980.44		$1,084.2899	$1,084.30	$1,084.25	$1,084.30