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	$236.51	4.317%	$246.7201	$246.72	$246.70	$246.70
Purchase #2	$75.35	4.262%	$78.5614	$78.56	$78.55	$78.60
Purchase #3	$11.68	3.630%	$12.104	$12.10	$12.10	$12.10
Purchase #4	$192.85	9.124%	$210.4456	$210.45	$210.45	$210.40
Purchase #5	$39.27	8.682%	$42.6794	$42.68	$42.70	$42.70
Purchase #6	$56.80	6.752%	$60.6351	$60.64	$60.65	$60.60
Purchase #7	$81.77	9.840%	$89.8162	$89.82	$89.80	$89.80
7 purchase totals =	$694.23		$740.9618	$740.97	$740.95	$740.90