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	$100.26	7.229%	$107.5078	$107.51	$107.50	$107.50
Purchase #2	$69.89	4.271%	$72.875	$72.88	$72.90	$72.90
Purchase #3	$59.41	5.521%	$62.69	$62.69	$62.70	$62.70
Purchase #4	$37.35	12.144%	$41.8858	$41.89	$41.90	$41.90
Purchase #5	$55.82	5.482%	$58.8801	$58.88	$58.90	$58.90
Purchase #6	$216.30	4.383%	$225.7804	$225.78	$225.80	$225.80
Purchase #7	$206.80	10.192%	$227.8771	$227.88	$227.90	$227.90
7 purchase totals =	$745.83		$797.4962	$797.51	$797.60	$797.60