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	$130.55	8.158%	$141.2003	$141.20	$141.20	$141.20
Purchase #2	$142.40	3.122%	$146.8457	$146.85	$146.85	$146.80
Purchase #3	$214.85	7.824%	$231.6599	$231.66	$231.65	$231.70
Purchase #4	$145.54	7.548%	$156.5254	$156.53	$156.55	$156.50
Purchase #5	$160.70	5.507%	$169.5497	$169.55	$169.55	$169.50
Purchase #6	$92.32	3.846%	$95.8706	$95.87	$95.85	$95.90
Purchase #7	$71.43	6.201%	$75.8594	$75.86	$75.85	$75.90
7 purchase totals =	$957.79		$1,017.5110	$1,017.52	$1,017.50	$1,017.50