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	$56.65	3.429%	$58.5925	$58.59	$58.60	$58.60
Purchase #2	$85.61	4.634%	$89.5772	$89.58	$89.60	$89.60
Purchase #3	$73.53	6.237%	$78.1161	$78.12	$78.10	$78.10
Purchase #4	$42.33	11.735%	$47.2974	$47.30	$47.30	$47.30
Purchase #5	$57.93	8.812%	$63.0348	$63.03	$63.05	$63.00
Purchase #6	$198.98	13.187%	$225.2195	$225.22	$225.20	$225.20
Purchase #7	$48.38	9.402%	$52.9287	$52.93	$52.95	$52.90
7 purchase totals =	$563.41		$614.7662	$614.77	$614.80	$614.70