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	$181.66	9.273%	$198.5053	$198.51	$198.50	$198.50
Purchase #2	$60.85	6.365%	$64.7231	$64.72	$64.70	$64.70
Purchase #3	$139.59	10.154%	$153.764	$153.76	$153.75	$153.80
Purchase #4	$235.42	7.872%	$253.9523	$253.95	$253.95	$254.00
Purchase #5	$86.65	3.804%	$89.9462	$89.95	$89.95	$89.90
Purchase #6	$103.58	13.360%	$117.4183	$117.42	$117.40	$117.40
Purchase #7	$30.77	3.661%	$31.8965	$31.90	$31.90	$31.90
7 purchase totals =	$838.52		$910.2057	$910.21	$910.15	$910.20