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	$225.84	8.865%	$245.8607	$245.86	$245.85	$245.90
Purchase #2	$159.47	8.665%	$173.2881	$173.29	$173.30	$173.30
Purchase #3	$155.72	8.215%	$168.5124	$168.51	$168.50	$168.50
Purchase #4	$155.43	7.837%	$167.611	$167.61	$167.60	$167.60
Purchase #5	$53.55	6.560%	$57.0629	$57.06	$57.05	$57.10
Purchase #6	$146.98	8.630%	$159.6644	$159.66	$159.65	$159.70
Purchase #7	$54.56	13.151%	$61.7352	$61.74	$61.75	$61.70
7 purchase totals =	$951.55		$1,033.7347	$1,033.73	$1,033.70	$1,033.80