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	$193.82	11.852%	$216.7915	$216.79	$216.80	$216.80
Purchase #2	$43.78	3.276%	$45.2142	$45.21	$45.20	$45.20
Purchase #3	$151.25	6.347%	$160.8498	$160.85	$160.85	$160.80
Purchase #4	$219.33	9.819%	$240.866	$240.87	$240.85	$240.90
Purchase #5	$174.76	12.437%	$196.4949	$196.49	$196.50	$196.50
Purchase #6	$209.74	7.460%	$225.3866	$225.39	$225.40	$225.40
Purchase #7	$227.67	6.745%	$243.0263	$243.03	$243.05	$243.00
7 purchase totals =	$1,220.35		$1,328.6293	$1,328.63	$1,328.65	$1,328.60