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	$177.31	7.868%	$191.2608	$191.26	$191.25	$191.30
Purchase #2	$86.48	3.504%	$89.5103	$89.51	$89.50	$89.50
Purchase #3	$20.66	3.856%	$21.4566	$21.46	$21.45	$21.50
Purchase #4	$245.59	9.815%	$269.6947	$269.69	$269.70	$269.70
Purchase #5	$53.48	8.464%	$58.0065	$58.01	$58.00	$58.00
Purchase #6	$217.79	4.374%	$227.3161	$227.32	$227.30	$227.30
Purchase #7	$38.85	5.414%	$40.9533	$40.95	$40.95	$41.00
7 purchase totals =	$840.16		$898.1983	$898.20	$898.15	$898.30