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	$85.64	5.620%	$90.453	$90.45	$90.45	$90.50
Purchase #2	$111.32	7.368%	$119.5221	$119.52	$119.50	$119.50
Purchase #3	$204.41	11.461%	$227.8374	$227.84	$227.85	$227.80
Purchase #4	$243.41	13.487%	$276.2387	$276.24	$276.25	$276.20
Purchase #5	$156.73	10.302%	$172.8763	$172.88	$172.90	$172.90
Purchase #6	$215.29	9.790%	$236.3669	$236.37	$236.35	$236.40
Purchase #7	$111.76	10.459%	$123.449	$123.45	$123.45	$123.40
7 purchase totals =	$1,128.56		$1,246.7434	$1,246.75	$1,246.75	$1,246.70