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	$48.68	12.550%	$54.7893	$54.79	$54.80	$54.80
Purchase #2	$173.79	13.115%	$196.5826	$196.58	$196.60	$196.60
Purchase #3	$212.26	8.173%	$229.608	$229.61	$229.60	$229.60
Purchase #4	$140.55	7.297%	$150.8059	$150.81	$150.80	$150.80
Purchase #5	$42.68	7.515%	$45.8874	$45.89	$45.90	$45.90
Purchase #6	$208.80	12.874%	$235.6809	$235.68	$235.70	$235.70
Purchase #7	$95.92	3.238%	$99.0259	$99.03	$99.05	$99.00
7 purchase totals =	$922.68		$1,012.3800	$1,012.39	$1,012.45	$1,012.40