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	$176.96	7.609%	$190.4249	$190.42	$190.40	$190.40
Purchase #2	$168.32	4.130%	$175.2716	$175.27	$175.25	$175.30
Purchase #3	$248.67	5.272%	$261.7799	$261.78	$261.80	$261.80
Purchase #4	$247.89	10.551%	$274.0449	$274.04	$274.05	$274.00
Purchase #5	$30.26	11.627%	$33.7783	$33.78	$33.80	$33.80
Purchase #6	$95.98	3.409%	$99.252	$99.25	$99.25	$99.30
Purchase #7	$56.84	10.580%	$62.8537	$62.85	$62.85	$62.90
7 purchase totals =	$1,024.92		$1,097.4053	$1,097.39	$1,097.40	$1,097.50