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	$58.73	5.518%	$61.9707	$61.97	$61.95	$62.00
Purchase #2	$127.86	3.863%	$132.7992	$132.80	$132.80	$132.80
Purchase #3	$111.61	11.598%	$124.5545	$124.55	$124.55	$124.60
Purchase #4	$67.77	4.408%	$70.7573	$70.76	$70.75	$70.80
Purchase #5	$65.46	7.835%	$70.5888	$70.59	$70.60	$70.60
Purchase #6	$189.42	12.811%	$213.6866	$213.69	$213.70	$213.70
Purchase #7	$79.70	11.872%	$89.162	$89.16	$89.15	$89.20
7 purchase totals =	$700.55		$763.5191	$763.52	$763.50	$763.70