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	$234.71	4.123%	$244.3871	$244.39	$244.40	$244.40
Purchase #2	$121.48	4.518%	$126.9685	$126.97	$126.95	$127.00
Purchase #3	$98.71	12.500%	$111.0488	$111.05	$111.05	$111.00
Purchase #4	$128.62	12.424%	$144.5997	$144.60	$144.60	$144.60
Purchase #5	$37.67	6.732%	$40.2059	$40.21	$40.20	$40.20
Purchase #6	$208.37	11.110%	$231.5199	$231.52	$231.50	$231.50
Purchase #7	$221.88	10.560%	$245.3105	$245.31	$245.30	$245.30
7 purchase totals =	$1,051.44		$1,144.0404	$1,144.05	$1,144.00	$1,144.00