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	$6.86	8.698%	$7.4567	$7.46	$7.45	$7.50
Purchase #2	$19.37	9.796%	$21.2675	$21.27	$21.25	$21.30
Purchase #3	$73.33	5.776%	$77.5655	$77.57	$77.55	$77.60
Purchase #4	$90.27	10.298%	$99.566	$99.57	$99.55	$99.60
Purchase #5	$212.96	9.204%	$232.5608	$232.56	$232.55	$232.60
Purchase #6	$78.33	3.813%	$81.3167	$81.32	$81.30	$81.30
Purchase #7	$155.57	12.684%	$175.3025	$175.30	$175.30	$175.30
7 purchase totals =	$636.69		$695.0357	$695.05	$694.95	$695.20