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	$203.37	11.801%	$227.3697	$227.37	$227.35	$227.40
Purchase #2	$55.73	7.557%	$59.9415	$59.94	$59.95	$59.90
Purchase #3	$127.31	6.688%	$135.8245	$135.82	$135.80	$135.80
Purchase #4	$74.31	10.846%	$82.3697	$82.37	$82.35	$82.40
Purchase #5	$231.35	9.807%	$254.0385	$254.04	$254.05	$254.00
Purchase #6	$152.29	11.208%	$169.3587	$169.36	$169.35	$169.40
Purchase #7	$168.27	8.102%	$181.9032	$181.90	$181.90	$181.90
7 purchase totals =	$1,012.63		$1,110.8058	$1,110.80	$1,110.75	$1,110.80