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	$147.65	3.505%	$152.8251	$152.83	$152.85	$152.80
Purchase #2	$170.65	4.827%	$178.8873	$178.89	$178.90	$178.90
Purchase #3	$31.60	5.200%	$33.2432	$33.24	$33.25	$33.20
Purchase #4	$159.71	9.466%	$174.8281	$174.83	$174.85	$174.80
Purchase #5	$54.56	6.839%	$58.2914	$58.29	$58.30	$58.30
Purchase #6	$40.74	4.483%	$42.5664	$42.57	$42.55	$42.60
Purchase #7	$250.54	10.169%	$276.0174	$276.02	$276.00	$276.00
7 purchase totals =	$855.45		$916.6589	$916.67	$916.70	$916.60