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	$91.43	10.575%	$101.0987	$101.10	$101.10	$101.10
Purchase #2	$208.27	4.871%	$218.4148	$218.41	$218.40	$218.40
Purchase #3	$83.85	6.317%	$89.1468	$89.15	$89.15	$89.10
Purchase #4	$21.60	11.477%	$24.079	$24.08	$24.10	$24.10
Purchase #5	$230.97	10.437%	$255.0763	$255.08	$255.10	$255.10
Purchase #6	$42.77	7.753%	$46.086	$46.09	$46.10	$46.10
Purchase #7	$33.60	8.811%	$36.5605	$36.56	$36.55	$36.60
7 purchase totals =	$712.49		$770.4621	$770.47	$770.50	$770.50