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	$148.44	13.112%	$167.9035	$167.90	$167.90	$167.90
Purchase #2	$111.48	10.536%	$123.2255	$123.23	$123.25	$123.20
Purchase #3	$14.92	6.358%	$15.8686	$15.87	$15.85	$15.90
Purchase #4	$202.49	3.683%	$209.9477	$209.95	$209.95	$209.90
Purchase #5	$249.90	12.636%	$281.4774	$281.48	$281.50	$281.50
Purchase #6	$135.75	12.634%	$152.9007	$152.90	$152.90	$152.90
Purchase #7	$143.59	10.148%	$158.1615	$158.16	$158.15	$158.20
7 purchase totals =	$1,006.57		$1,109.4849	$1,109.49	$1,109.50	$1,109.50