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	$207.32	4.640%	$216.9396	$216.94	$216.95	$216.90
Purchase #2	$130.63	10.566%	$144.4324	$144.43	$144.45	$144.40
Purchase #3	$200.33	13.704%	$227.7832	$227.78	$227.80	$227.80
Purchase #4	$49.29	8.764%	$53.6098	$53.61	$53.60	$53.60
Purchase #5	$32.88	12.549%	$37.0061	$37.01	$37.00	$37.00
Purchase #6	$5.44	11.607%	$6.0714	$6.07	$6.05	$6.10
Purchase #7	$208.32	9.808%	$228.752	$228.75	$228.75	$228.80
7 purchase totals =	$834.21		$914.5945	$914.59	$914.60	$914.60