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	$94.96	9.118%	$103.6185	$103.62	$103.60	$103.60
Purchase #2	$56.69	4.742%	$59.3782	$59.38	$59.40	$59.40
Purchase #3	$175.56	10.845%	$194.5995	$194.60	$194.60	$194.60
Purchase #4	$165.61	8.873%	$180.3046	$180.30	$180.30	$180.30
Purchase #5	$133.59	12.229%	$149.9267	$149.93	$149.95	$149.90
Purchase #6	$203.96	8.384%	$221.06	$221.06	$221.05	$221.10
Purchase #7	$232.29	10.587%	$256.8825	$256.88	$256.90	$256.90
7 purchase totals =	$1,062.66		$1,165.7700	$1,165.77	$1,165.80	$1,165.80