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	$156.60	7.540%	$168.4076	$168.41	$168.40	$168.40
Purchase #2	$24.96	4.634%	$26.1166	$26.12	$26.10	$26.10
Purchase #3	$41.61	7.582%	$44.7649	$44.76	$44.75	$44.80
Purchase #4	$77.91	4.705%	$81.5757	$81.58	$81.60	$81.60
Purchase #5	$120.89	9.116%	$131.9103	$131.91	$131.90	$131.90
Purchase #6	$109.62	5.854%	$116.0372	$116.04	$116.05	$116.00
Purchase #7	$78.83	13.224%	$89.2545	$89.25	$89.25	$89.30
7 purchase totals =	$610.42		$658.0668	$658.07	$658.05	$658.10