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	$146.87	6.237%	$156.0303	$156.03	$156.05	$156.00
Purchase #2	$141.26	6.527%	$150.48	$150.48	$150.50	$150.50
Purchase #3	$167.70	10.726%	$185.6875	$185.69	$185.70	$185.70
Purchase #4	$46.76	12.262%	$52.4937	$52.49	$52.50	$52.50
Purchase #5	$221.60	10.750%	$245.422	$245.42	$245.40	$245.40
Purchase #6	$116.49	12.547%	$131.106	$131.11	$131.10	$131.10
Purchase #7	$101.77	11.645%	$113.6211	$113.62	$113.60	$113.60
7 purchase totals =	$942.45		$1,034.8406	$1,034.84	$1,034.85	$1,034.80