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	$148.39	11.539%	$165.5127	$165.51	$165.50	$165.50
Purchase #2	$144.50	12.720%	$162.8804	$162.88	$162.90	$162.90
Purchase #3	$199.63	4.302%	$208.2181	$208.22	$208.20	$208.20
Purchase #4	$212.35	11.152%	$236.0313	$236.03	$236.05	$236.00
Purchase #5	$79.83	10.830%	$88.4756	$88.48	$88.50	$88.50
Purchase #6	$6.79	12.429%	$7.6339	$7.63	$7.65	$7.60
Purchase #7	$64.64	12.577%	$72.7698	$72.77	$72.75	$72.80
7 purchase totals =	$856.13		$941.5218	$941.52	$941.55	$941.50