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	$100.86	4.218%	$105.1143	$105.11	$105.10	$105.10
Purchase #2	$80.29	13.148%	$90.8465	$90.85	$90.85	$90.80
Purchase #3	$216.53	13.150%	$245.0037	$245.00	$245.00	$245.00
Purchase #4	$211.51	6.551%	$225.366	$225.37	$225.35	$225.40
Purchase #5	$143.77	12.221%	$161.3401	$161.34	$161.35	$161.30
Purchase #6	$147.55	4.377%	$154.0083	$154.01	$154.00	$154.00
Purchase #7	$212.25	7.595%	$228.3704	$228.37	$228.35	$228.40
7 purchase totals =	$1,112.76		$1,210.0493	$1,210.05	$1,210.00	$1,210.00