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	$10.44	3.656%	$10.8217	$10.82	$10.80	$10.80
Purchase #2	$105.46	8.765%	$114.7036	$114.70	$114.70	$114.70
Purchase #3	$215.77	6.380%	$229.5361	$229.54	$229.55	$229.50
Purchase #4	$237.94	10.756%	$263.5328	$263.53	$263.55	$263.50
Purchase #5	$157.73	11.329%	$175.5992	$175.60	$175.60	$175.60
Purchase #6	$75.50	7.384%	$81.0749	$81.07	$81.05	$81.10
Purchase #7	$174.63	6.746%	$186.4105	$186.41	$186.40	$186.40
7 purchase totals =	$977.47		$1,061.6788	$1,061.67	$1,061.65	$1,061.60