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	$53.70	11.430%	$59.8379	$59.84	$59.85	$59.80
Purchase #2	$81.31	6.692%	$86.7513	$86.75	$86.75	$86.80
Purchase #3	$220.70	4.443%	$230.5057	$230.51	$230.50	$230.50
Purchase #4	$33.76	8.764%	$36.7187	$36.72	$36.70	$36.70
Purchase #5	$161.29	11.657%	$180.0916	$180.09	$180.10	$180.10
Purchase #6	$31.73	6.443%	$33.7744	$33.77	$33.75	$33.80
Purchase #7	$227.81	12.226%	$255.6621	$255.66	$255.65	$255.70
7 purchase totals =	$810.30		$883.3417	$883.34	$883.30	$883.40