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	$86.66	3.427%	$89.6298	$89.63	$89.65	$89.60
Purchase #2	$161.91	6.793%	$172.9085	$172.91	$172.90	$172.90
Purchase #3	$199.94	3.810%	$207.5577	$207.56	$207.55	$207.60
Purchase #4	$207.59	6.738%	$221.5774	$221.58	$221.60	$221.60
Purchase #5	$20.27	6.593%	$21.6064	$21.61	$21.60	$21.60
Purchase #6	$231.96	3.799%	$240.7722	$240.77	$240.75	$240.80
Purchase #7	$29.43	6.831%	$31.4404	$31.44	$31.45	$31.40
7 purchase totals =	$937.76		$985.4924	$985.50	$985.50	$985.50