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	$73.57	3.596%	$76.2156	$76.22	$76.20	$76.20
Purchase #2	$151.87	10.835%	$168.3251	$168.33	$168.35	$168.30
Purchase #3	$208.27	9.485%	$228.0244	$228.02	$228.00	$228.00
Purchase #4	$100.72	8.808%	$109.5914	$109.59	$109.60	$109.60
Purchase #5	$247.97	4.547%	$259.2452	$259.25	$259.25	$259.20
Purchase #6	$37.59	8.285%	$40.7043	$40.70	$40.70	$40.70
Purchase #7	$155.91	11.108%	$173.2285	$173.23	$173.25	$173.20
7 purchase totals =	$975.90		$1,055.3345	$1,055.34	$1,055.35	$1,055.20