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	$92.87	13.452%	$105.3629	$105.36	$105.35	$105.40
Purchase #2	$115.52	3.796%	$119.9051	$119.91	$119.90	$119.90
Purchase #3	$95.79	11.128%	$106.4495	$106.45	$106.45	$106.40
Purchase #4	$172.90	7.289%	$185.5027	$185.50	$185.50	$185.50
Purchase #5	$165.40	4.664%	$173.1143	$173.11	$173.10	$173.10
Purchase #6	$235.40	9.828%	$258.5351	$258.54	$258.55	$258.50
Purchase #7	$85.75	13.522%	$97.3451	$97.35	$97.35	$97.30
7 purchase totals =	$963.63		$1,046.2147	$1,046.22	$1,046.20	$1,046.10