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	$228.70	13.140%	$258.7512	$258.75	$258.75	$258.80
Purchase #2	$96.46	3.544%	$99.8785	$99.88	$99.90	$99.90
Purchase #3	$93.66	6.635%	$99.8743	$99.87	$99.85	$99.90
Purchase #4	$127.27	13.313%	$144.2135	$144.21	$144.20	$144.20
Purchase #5	$178.66	11.242%	$198.745	$198.75	$198.75	$198.70
Purchase #6	$123.72	13.649%	$140.6065	$140.61	$140.60	$140.60
Purchase #7	$164.93	6.792%	$176.132	$176.13	$176.15	$176.10
7 purchase totals =	$1,013.40		$1,118.2010	$1,118.20	$1,118.20	$1,118.20