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	$212.62	13.620%	$241.5788	$241.58	$241.60	$241.60
Purchase #2	$243.27	10.119%	$267.8865	$267.89	$267.90	$267.90
Purchase #3	$241.96	5.328%	$254.8516	$254.85	$254.85	$254.90
Purchase #4	$96.45	9.535%	$105.6465	$105.65	$105.65	$105.60
Purchase #5	$154.78	9.803%	$169.9531	$169.95	$169.95	$170.00
Purchase #6	$64.30	11.419%	$71.6424	$71.64	$71.65	$71.60
Purchase #7	$77.87	10.325%	$85.9101	$85.91	$85.90	$85.90
7 purchase totals =	$1,091.25		$1,197.4690	$1,197.47	$1,197.50	$1,197.50