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	$77.76	12.843%	$87.7467	$87.75	$87.75	$87.70
Purchase #2	$174.72	12.526%	$196.6054	$196.61	$196.60	$196.60
Purchase #3	$159.39	13.346%	$180.6622	$180.66	$180.65	$180.70
Purchase #4	$223.48	5.476%	$235.7178	$235.72	$235.70	$235.70
Purchase #5	$111.33	11.108%	$123.6965	$123.70	$123.70	$123.70
Purchase #6	$37.66	3.656%	$39.0368	$39.04	$39.05	$39.00
Purchase #7	$171.31	8.763%	$186.3219	$186.32	$186.30	$186.30
7 purchase totals =	$955.65		$1,049.7873	$1,049.80	$1,049.75	$1,049.70