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	$36.93	3.526%	$38.2322	$38.23	$38.25	$38.20
Purchase #2	$224.59	10.237%	$247.5813	$247.58	$247.60	$247.60
Purchase #3	$188.93	12.508%	$212.5614	$212.56	$212.55	$212.60
Purchase #4	$29.48	6.273%	$31.3293	$31.33	$31.35	$31.30
Purchase #5	$163.39	3.793%	$169.5874	$169.59	$169.60	$169.60
Purchase #6	$53.89	10.515%	$59.5565	$59.56	$59.55	$59.60
Purchase #7	$20.85	10.124%	$22.9609	$22.96	$22.95	$23.00
7 purchase totals =	$718.06		$781.8090	$781.81	$781.85	$781.90