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	$183.80	7.129%	$196.9031	$196.90	$196.90	$196.90
Purchase #2	$159.35	10.742%	$176.4674	$176.47	$176.45	$176.50
Purchase #3	$59.80	10.432%	$66.0383	$66.04	$66.05	$66.00
Purchase #4	$22.82	12.344%	$25.6369	$25.64	$25.65	$25.60
Purchase #5	$248.44	3.336%	$256.728	$256.73	$256.75	$256.70
Purchase #6	$105.59	8.497%	$114.562	$114.56	$114.55	$114.60
Purchase #7	$145.88	13.795%	$166.0041	$166.00	$166.00	$166.00
7 purchase totals =	$925.68		$1,002.3398	$1,002.34	$1,002.35	$1,002.30