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	$250.61	9.709%	$274.9417	$274.94	$274.95	$274.90
Purchase #2	$106.57	7.300%	$114.3496	$114.35	$114.35	$114.30
Purchase #3	$42.59	13.591%	$48.3784	$48.38	$48.40	$48.40
Purchase #4	$163.27	4.182%	$170.098	$170.10	$170.10	$170.10
Purchase #5	$104.44	6.781%	$111.5221	$111.52	$111.50	$111.50
Purchase #6	$32.48	3.510%	$33.62	$33.62	$33.60	$33.60
Purchase #7	$102.77	6.851%	$109.8108	$109.81	$109.80	$109.80
7 purchase totals =	$802.73		$862.7206	$862.72	$862.70	$862.60