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	$59.47	3.490%	$61.5455	$61.55	$61.55	$61.50
Purchase #2	$131.63	6.765%	$140.5348	$140.53	$140.55	$140.50
Purchase #3	$78.31	10.486%	$86.5216	$86.52	$86.50	$86.50
Purchase #4	$33.80	6.766%	$36.0869	$36.09	$36.10	$36.10
Purchase #5	$98.83	7.581%	$106.3223	$106.32	$106.30	$106.30
Purchase #6	$134.97	3.633%	$139.8735	$139.87	$139.85	$139.90
Purchase #7	$36.70	6.561%	$39.1079	$39.11	$39.10	$39.10
7 purchase totals =	$573.71		$609.9925	$609.99	$609.95	$609.90