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	$193.74	3.686%	$200.8813	$200.88	$200.90	$200.90
Purchase #2	$73.53	13.676%	$83.586	$83.59	$83.60	$83.60
Purchase #3	$146.47	4.122%	$152.5075	$152.51	$152.50	$152.50
Purchase #4	$107.29	13.873%	$122.1743	$122.17	$122.15	$122.20
Purchase #5	$214.42	13.115%	$242.5412	$242.54	$242.55	$242.50
Purchase #6	$188.86	11.455%	$210.4939	$210.49	$210.50	$210.50
Purchase #7	$121.70	7.713%	$131.0867	$131.09	$131.10	$131.10
7 purchase totals =	$1,046.01		$1,143.2709	$1,143.27	$1,143.30	$1,143.30