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	$201.72	11.183%	$224.2783	$224.28	$224.30	$224.30
Purchase #2	$145.79	4.475%	$152.3141	$152.31	$152.30	$152.30
Purchase #3	$175.33	7.503%	$188.485	$188.49	$188.50	$188.50
Purchase #4	$52.28	4.293%	$54.5244	$54.52	$54.50	$54.50
Purchase #5	$164.37	4.439%	$171.6664	$171.67	$171.65	$171.70
Purchase #6	$244.50	12.489%	$275.0356	$275.04	$275.05	$275.00
Purchase #7	$171.84	9.395%	$187.9844	$187.98	$188.00	$188.00
7 purchase totals =	$1,155.83		$1,254.2882	$1,254.29	$1,254.30	$1,254.30