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	$71.78	5.252%	$75.5499	$75.55	$75.55	$75.50
Purchase #2	$53.27	4.844%	$55.8504	$55.85	$55.85	$55.90
Purchase #3	$70.27	5.804%	$74.3485	$74.35	$74.35	$74.30
Purchase #4	$135.76	11.218%	$150.9896	$150.99	$151.00	$151.00
Purchase #5	$184.66	3.253%	$190.667	$190.67	$190.65	$190.70
Purchase #6	$85.49	4.261%	$89.1327	$89.13	$89.15	$89.10
Purchase #7	$80.66	9.759%	$88.5316	$88.53	$88.55	$88.50
7 purchase totals =	$681.89		$725.0697	$725.07	$725.10	$725.00