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	$136.27	3.646%	$141.2384	$141.24	$141.25	$141.20
Purchase #2	$191.86	13.177%	$217.1414	$217.14	$217.15	$217.10
Purchase #3	$161.72	6.118%	$171.614	$171.61	$171.60	$171.60
Purchase #4	$152.52	9.432%	$166.9057	$166.91	$166.90	$166.90
Purchase #5	$24.65	4.158%	$25.6749	$25.67	$25.65	$25.70
Purchase #6	$208.29	9.324%	$227.711	$227.71	$227.70	$227.70
Purchase #7	$92.69	13.797%	$105.4784	$105.48	$105.50	$105.50
7 purchase totals =	$968.00		$1,055.7638	$1,055.76	$1,055.75	$1,055.70