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	$196.56	13.427%	$222.9521	$222.95	$222.95	$223.00
Purchase #2	$77.45	11.778%	$86.5721	$86.57	$86.55	$86.60
Purchase #3	$77.82	11.294%	$86.609	$86.61	$86.60	$86.60
Purchase #4	$27.89	7.507%	$29.9837	$29.98	$30.00	$30.00
Purchase #5	$137.98	11.229%	$153.4738	$153.47	$153.45	$153.50
Purchase #6	$78.64	6.116%	$83.4496	$83.45	$83.45	$83.40
Purchase #7	$80.86	4.279%	$84.32	$84.32	$84.30	$84.30
7 purchase totals =	$677.20		$747.3603	$747.35	$747.30	$747.40