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	$78.50	5.836%	$83.0813	$83.08	$83.10	$83.10
Purchase #2	$196.89	9.741%	$216.0691	$216.07	$216.05	$216.10
Purchase #3	$66.91	7.567%	$71.9731	$71.97	$71.95	$72.00
Purchase #4	$203.88	9.593%	$223.4382	$223.44	$223.45	$223.40
Purchase #5	$42.43	10.665%	$46.9552	$46.96	$46.95	$47.00
Purchase #6	$96.88	10.228%	$106.7889	$106.79	$106.80	$106.80
Purchase #7	$34.28	13.852%	$39.0285	$39.03	$39.05	$39.00
7 purchase totals =	$719.77		$787.3343	$787.34	$787.35	$787.40