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	$105.47	4.153%	$109.8502	$109.85	$109.85	$109.90
Purchase #2	$172.70	5.543%	$182.2728	$182.27	$182.25	$182.30
Purchase #3	$93.25	12.698%	$105.0909	$105.09	$105.10	$105.10
Purchase #4	$222.93	10.232%	$245.7402	$245.74	$245.75	$245.70
Purchase #5	$125.64	5.760%	$132.8769	$132.88	$132.90	$132.90
Purchase #6	$72.51	6.643%	$77.3268	$77.33	$77.35	$77.30
Purchase #7	$214.94	13.851%	$244.7113	$244.71	$244.70	$244.70
7 purchase totals =	$1,007.44		$1,097.8691	$1,097.87	$1,097.90	$1,097.90