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	$202.65	9.618%	$222.1409	$222.14	$222.15	$222.10
Purchase #2	$34.66	13.480%	$39.3322	$39.33	$39.35	$39.30
Purchase #3	$247.35	6.672%	$263.8532	$263.85	$263.85	$263.90
Purchase #4	$65.43	8.531%	$71.0118	$71.01	$71.00	$71.00
Purchase #5	$21.34	5.185%	$22.4465	$22.45	$22.45	$22.40
Purchase #6	$108.99	13.716%	$123.9391	$123.94	$123.95	$123.90
Purchase #7	$165.96	11.572%	$185.1649	$185.16	$185.15	$185.20
7 purchase totals =	$846.38		$927.8886	$927.88	$927.90	$927.80