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	$163.98	12.853%	$185.0563	$185.06	$185.05	$185.10
Purchase #2	$36.29	7.787%	$39.1159	$39.12	$39.10	$39.10
Purchase #3	$121.92	11.110%	$135.4653	$135.47	$135.45	$135.50
Purchase #4	$139.45	8.639%	$151.4971	$151.50	$151.50	$151.50
Purchase #5	$248.31	13.324%	$281.3948	$281.39	$281.40	$281.40
Purchase #6	$245.25	4.276%	$255.7369	$255.74	$255.75	$255.70
Purchase #7	$140.72	5.318%	$148.2035	$148.20	$148.20	$148.20
7 purchase totals =	$1,095.92		$1,196.4698	$1,196.48	$1,196.45	$1,196.50