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	$37.95	5.549%	$40.0558	$40.06	$40.05	$40.10
Purchase #2	$11.87	9.195%	$12.9614	$12.96	$12.95	$13.00
Purchase #3	$11.53	13.368%	$13.0713	$13.07	$13.05	$13.10
Purchase #4	$87.48	13.215%	$99.0405	$99.04	$99.05	$99.00
Purchase #5	$229.53	11.332%	$255.5403	$255.54	$255.55	$255.50
Purchase #6	$150.34	6.643%	$160.3271	$160.33	$160.35	$160.30
Purchase #7	$81.49	6.226%	$86.5636	$86.56	$86.55	$86.60
7 purchase totals =	$610.19		$667.5600	$667.56	$667.55	$667.60