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	$211.65	3.700%	$219.4811	$219.48	$219.50	$219.50
Purchase #2	$128.46	8.559%	$139.4549	$139.45	$139.45	$139.50
Purchase #3	$130.27	13.175%	$147.4331	$147.43	$147.45	$147.40
Purchase #4	$188.72	8.111%	$204.0271	$204.03	$204.05	$204.00
Purchase #5	$80.91	5.253%	$85.1602	$85.16	$85.15	$85.20
Purchase #6	$143.73	10.310%	$158.5486	$158.55	$158.55	$158.50
Purchase #7	$9.76	8.502%	$10.5898	$10.59	$10.60	$10.60
7 purchase totals =	$893.50		$964.6948	$964.69	$964.75	$964.70