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	$223.57	8.199%	$241.9005	$241.90	$241.90	$241.90
Purchase #2	$79.73	13.319%	$90.3492	$90.35	$90.35	$90.30
Purchase #3	$158.69	8.576%	$172.2993	$172.30	$172.30	$172.30
Purchase #4	$173.50	6.675%	$185.0811	$185.08	$185.10	$185.10
Purchase #5	$168.93	12.356%	$189.803	$189.80	$189.80	$189.80
Purchase #6	$89.60	6.208%	$95.1624	$95.16	$95.15	$95.20
Purchase #7	$204.90	4.579%	$214.2824	$214.28	$214.30	$214.30
7 purchase totals =	$1,098.92		$1,188.8779	$1,188.87	$1,188.90	$1,188.90