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	$183.38	13.521%	$208.1748	$208.17	$208.15	$208.20
Purchase #2	$231.69	13.760%	$263.5705	$263.57	$263.55	$263.60
Purchase #3	$178.35	4.255%	$185.9388	$185.94	$185.95	$185.90
Purchase #4	$19.66	10.147%	$21.6549	$21.65	$21.65	$21.70
Purchase #5	$80.58	11.361%	$89.7347	$89.73	$89.75	$89.70
Purchase #6	$215.44	7.581%	$231.7725	$231.77	$231.75	$231.80
Purchase #7	$88.74	7.661%	$95.5384	$95.54	$95.55	$95.50
7 purchase totals =	$997.84		$1,096.3846	$1,096.37	$1,096.35	$1,096.40