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	$47.88	7.841%	$51.6343	$51.63	$51.65	$51.60
Purchase #2	$74.33	5.672%	$78.546	$78.55	$78.55	$78.50
Purchase #3	$27.43	3.296%	$28.3341	$28.33	$28.35	$28.30
Purchase #4	$18.38	9.537%	$20.1329	$20.13	$20.15	$20.10
Purchase #5	$14.34	6.248%	$15.236	$15.24	$15.25	$15.20
Purchase #6	$57.48	13.574%	$65.2823	$65.28	$65.30	$65.30
Purchase #7	$215.77	8.348%	$233.7825	$233.78	$233.80	$233.80
7 purchase totals =	$455.61		$492.9481	$492.94	$493.05	$492.80