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	$113.96	8.680%	$123.8517	$123.85	$123.85	$123.90
Purchase #2	$55.39	12.434%	$62.2772	$62.28	$62.30	$62.30
Purchase #3	$246.30	4.253%	$256.7751	$256.78	$256.80	$256.80
Purchase #4	$159.34	7.137%	$170.7121	$170.71	$170.70	$170.70
Purchase #5	$115.84	6.605%	$123.4912	$123.49	$123.50	$123.50
Purchase #6	$59.44	13.363%	$67.383	$67.38	$67.40	$67.40
Purchase #7	$111.87	6.557%	$119.2053	$119.21	$119.20	$119.20
7 purchase totals =	$862.14		$923.6956	$923.70	$923.75	$923.80