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	$48.55	9.632%	$53.2263	$53.23	$53.25	$53.20
Purchase #2	$206.53	9.659%	$226.4787	$226.48	$226.50	$226.50
Purchase #3	$200.62	6.607%	$213.875	$213.88	$213.90	$213.90
Purchase #4	$41.94	9.131%	$45.7695	$45.77	$45.75	$45.80
Purchase #5	$89.69	10.625%	$99.2196	$99.22	$99.20	$99.20
Purchase #6	$202.36	13.602%	$229.885	$229.89	$229.90	$229.90
Purchase #7	$78.37	4.319%	$81.7548	$81.75	$81.75	$81.80
7 purchase totals =	$868.06		$950.2089	$950.22	$950.25	$950.30