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	$5.81	9.356%	$6.3536	$6.35	$6.35	$6.40
Purchase #2	$29.39	7.181%	$31.5005	$31.50	$31.50	$31.50
Purchase #3	$37.44	7.213%	$40.1405	$40.14	$40.15	$40.10
Purchase #4	$96.41	4.597%	$100.842	$100.84	$100.85	$100.80
Purchase #5	$229.62	13.771%	$261.241	$261.24	$261.25	$261.20
Purchase #6	$200.82	4.482%	$209.8208	$209.82	$209.80	$209.80
Purchase #7	$211.81	6.545%	$225.673	$225.67	$225.65	$225.70
7 purchase totals =	$811.30		$875.5714	$875.56	$875.55	$875.50