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	$32.62	7.478%	$35.0593	$35.06	$35.05	$35.10
Purchase #2	$34.95	5.213%	$36.7719	$36.77	$36.75	$36.80
Purchase #3	$78.49	8.837%	$85.4262	$85.43	$85.45	$85.40
Purchase #4	$86.82	6.847%	$92.7646	$92.76	$92.75	$92.80
Purchase #5	$196.54	13.268%	$222.6169	$222.62	$222.60	$222.60
Purchase #6	$63.72	6.234%	$67.6923	$67.69	$67.70	$67.70
Purchase #7	$222.84	13.672%	$253.3067	$253.31	$253.30	$253.30
7 purchase totals =	$715.98		$793.6379	$793.64	$793.60	$793.70