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	$41.72	11.361%	$46.4598	$46.46	$46.45	$46.50
Purchase #2	$54.80	12.699%	$61.7591	$61.76	$61.75	$61.80
Purchase #3	$216.49	7.683%	$233.1229	$233.12	$233.10	$233.10
Purchase #4	$207.49	5.492%	$218.8854	$218.89	$218.90	$218.90
Purchase #5	$50.79	11.302%	$56.5303	$56.53	$56.55	$56.50
Purchase #6	$102.97	9.312%	$112.5586	$112.56	$112.55	$112.60
Purchase #7	$196.72	13.459%	$223.1965	$223.20	$223.20	$223.20
7 purchase totals =	$870.98		$952.5126	$952.52	$952.50	$952.60