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	$62.62	5.125%	$65.8293	$65.83	$65.85	$65.80
Purchase #2	$98.81	12.453%	$111.1148	$111.11	$111.10	$111.10
Purchase #3	$112.70	6.244%	$119.737	$119.74	$119.75	$119.70
Purchase #4	$248.29	4.726%	$260.0242	$260.02	$260.00	$260.00
Purchase #5	$190.83	12.320%	$214.3403	$214.34	$214.35	$214.30
Purchase #6	$208.49	6.592%	$222.2337	$222.23	$222.25	$222.20
Purchase #7	$58.63	11.420%	$65.3255	$65.33	$65.35	$65.30
7 purchase totals =	$980.37		$1,058.6048	$1,058.60	$1,058.65	$1,058.40