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	$58.54	6.563%	$62.382	$62.38	$62.40	$62.40
Purchase #2	$72.52	11.458%	$80.8293	$80.83	$80.85	$80.80
Purchase #3	$27.67	8.186%	$29.9351	$29.94	$29.95	$29.90
Purchase #4	$66.59	7.289%	$71.4437	$71.44	$71.45	$71.40
Purchase #5	$31.57	3.360%	$32.6308	$32.63	$32.65	$32.60
Purchase #6	$29.50	8.343%	$31.9612	$31.96	$31.95	$32.00
Purchase #7	$11.61	11.582%	$12.9547	$12.95	$12.95	$13.00
7 purchase totals =	$298.00		$322.1368	$322.13	$322.20	$322.10