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	$196.45	8.130%	$212.4214	$212.42	$212.40	$212.40
Purchase #2	$82.45	4.155%	$85.8758	$85.88	$85.90	$85.90
Purchase #3	$140.67	4.283%	$146.6949	$146.69	$146.70	$146.70
Purchase #4	$145.54	8.546%	$157.9778	$157.98	$158.00	$158.00
Purchase #5	$118.36	4.386%	$123.5513	$123.55	$123.55	$123.60
Purchase #6	$6.99	4.122%	$7.2781	$7.28	$7.30	$7.30
Purchase #7	$108.42	9.252%	$118.451	$118.45	$118.45	$118.50
7 purchase totals =	$798.88		$852.2503	$852.25	$852.30	$852.40