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	$132.43	11.461%	$147.6078	$147.61	$147.60	$147.60
Purchase #2	$137.58	11.662%	$153.6246	$153.62	$153.60	$153.60
Purchase #3	$162.78	5.244%	$171.3162	$171.32	$171.30	$171.30
Purchase #4	$69.78	11.641%	$77.9031	$77.90	$77.90	$77.90
Purchase #5	$59.39	3.140%	$61.2548	$61.25	$61.25	$61.30
Purchase #6	$16.69	9.445%	$18.2664	$18.27	$18.25	$18.30
Purchase #7	$199.48	3.259%	$205.9811	$205.98	$206.00	$206.00
7 purchase totals =	$778.13		$835.9540	$835.95	$835.90	$836.00