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	$190.60	10.496%	$210.6054	$210.61	$210.60	$210.60
Purchase #2	$50.29	8.159%	$54.3932	$54.39	$54.40	$54.40
Purchase #3	$170.47	6.154%	$180.9607	$180.96	$180.95	$181.00
Purchase #4	$48.40	9.230%	$52.8673	$52.87	$52.85	$52.90
Purchase #5	$97.43	6.567%	$103.8282	$103.83	$103.85	$103.80
Purchase #6	$106.34	8.180%	$115.0386	$115.04	$115.05	$115.00
Purchase #7	$183.89	6.670%	$196.1555	$196.16	$196.15	$196.20
7 purchase totals =	$847.42		$913.8489	$913.86	$913.85	$913.90