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	$76.90	8.497%	$83.4342	$83.43	$83.45	$83.40
Purchase #2	$162.49	9.538%	$177.9883	$177.99	$178.00	$178.00
Purchase #3	$81.33	11.358%	$90.5675	$90.57	$90.55	$90.60
Purchase #4	$173.98	9.377%	$190.2941	$190.29	$190.30	$190.30
Purchase #5	$244.61	11.122%	$271.8155	$271.82	$271.80	$271.80
Purchase #6	$60.90	5.348%	$64.1569	$64.16	$64.15	$64.20
Purchase #7	$121.72	6.362%	$129.4638	$129.46	$129.45	$129.50
7 purchase totals =	$921.93		$1,007.7203	$1,007.72	$1,007.70	$1,007.80