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	$104.65	8.808%	$113.8676	$113.87	$113.85	$113.90
Purchase #2	$37.97	12.623%	$42.763	$42.76	$42.75	$42.80
Purchase #3	$91.64	4.236%	$95.5219	$95.52	$95.50	$95.50
Purchase #4	$59.57	5.299%	$62.7266	$62.73	$62.75	$62.70
Purchase #5	$95.42	3.505%	$98.7645	$98.76	$98.75	$98.80
Purchase #6	$161.56	4.473%	$168.7866	$168.79	$168.80	$168.80
Purchase #7	$58.95	12.114%	$66.0912	$66.09	$66.10	$66.10
7 purchase totals =	$609.76		$648.5214	$648.52	$648.50	$648.60