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	$75.64	12.572%	$85.1495	$85.15	$85.15	$85.10
Purchase #2	$99.98	9.363%	$109.3411	$109.34	$109.35	$109.30
Purchase #3	$10.87	10.793%	$12.0432	$12.04	$12.05	$12.00
Purchase #4	$93.80	8.710%	$101.97	$101.97	$101.95	$102.00
Purchase #5	$102.80	13.534%	$116.713	$116.71	$116.70	$116.70
Purchase #6	$171.86	4.675%	$179.8945	$179.89	$179.90	$179.90
Purchase #7	$246.34	9.791%	$270.4591	$270.46	$270.45	$270.50
7 purchase totals =	$801.29		$875.5704	$875.56	$875.55	$875.50