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	$205.69	9.606%	$225.4486	$225.45	$225.45	$225.40
Purchase #2	$139.71	5.596%	$147.5282	$147.53	$147.55	$147.50
Purchase #3	$180.27	11.432%	$200.8785	$200.88	$200.90	$200.90
Purchase #4	$60.86	10.485%	$67.2412	$67.24	$67.25	$67.20
Purchase #5	$229.41	3.767%	$238.0519	$238.05	$238.05	$238.10
Purchase #6	$199.88	7.823%	$215.5166	$215.52	$215.50	$215.50
Purchase #7	$209.26	4.482%	$218.639	$218.64	$218.65	$218.60
7 purchase totals =	$1,225.08		$1,313.3040	$1,313.31	$1,313.35	$1,313.20