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	$104.92	6.358%	$111.5908	$111.59	$111.60	$111.60
Purchase #2	$167.76	13.435%	$190.2986	$190.30	$190.30	$190.30
Purchase #3	$122.64	10.381%	$135.3713	$135.37	$135.35	$135.40
Purchase #4	$139.79	13.731%	$158.9846	$158.98	$159.00	$159.00
Purchase #5	$152.79	11.678%	$170.6328	$170.63	$170.65	$170.60
Purchase #6	$238.35	7.532%	$256.3025	$256.30	$256.30	$256.30
Purchase #7	$72.86	7.741%	$78.5001	$78.50	$78.50	$78.50
7 purchase totals =	$999.11		$1,101.6807	$1,101.67	$1,101.70	$1,101.70