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	$148.64	13.590%	$168.8402	$168.84	$168.85	$168.80
Purchase #2	$26.55	3.510%	$27.4819	$27.48	$27.50	$27.50
Purchase #3	$19.38	6.209%	$20.5833	$20.58	$20.60	$20.60
Purchase #4	$86.69	13.634%	$98.5093	$98.51	$98.50	$98.50
Purchase #5	$129.50	10.328%	$142.8748	$142.87	$142.85	$142.90
Purchase #6	$139.36	9.332%	$152.3651	$152.37	$152.35	$152.40
Purchase #7	$93.26	13.243%	$105.6104	$105.61	$105.60	$105.60
7 purchase totals =	$643.38		$716.2650	$716.26	$716.25	$716.30