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	$46.93	9.241%	$51.2668	$51.27	$51.25	$51.30
Purchase #2	$85.68	4.525%	$89.557	$89.56	$89.55	$89.60
Purchase #3	$207.69	7.282%	$222.814	$222.81	$222.80	$222.80
Purchase #4	$108.62	6.824%	$116.0322	$116.03	$116.05	$116.00
Purchase #5	$228.93	7.307%	$245.6579	$245.66	$245.65	$245.70
Purchase #6	$245.81	4.684%	$257.3237	$257.32	$257.30	$257.30
Purchase #7	$45.44	8.353%	$49.2356	$49.24	$49.25	$49.20
7 purchase totals =	$969.10		$1,031.8872	$1,031.89	$1,031.85	$1,031.90