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	$81.73	4.689%	$85.5623	$85.56	$85.55	$85.60
Purchase #2	$54.87	11.198%	$61.0143	$61.01	$61.00	$61.00
Purchase #3	$45.61	13.760%	$51.8859	$51.89	$51.90	$51.90
Purchase #4	$40.58	5.605%	$42.8545	$42.85	$42.85	$42.90
Purchase #5	$214.98	9.218%	$234.7969	$234.80	$234.80	$234.80
Purchase #6	$114.62	11.610%	$127.9274	$127.93	$127.95	$127.90
Purchase #7	$133.27	10.277%	$146.9662	$146.97	$146.95	$147.00
7 purchase totals =	$685.66		$751.0075	$751.01	$751.00	$751.10