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	$247.42	9.556%	$271.0635	$271.06	$271.05	$271.10
Purchase #2	$18.37	4.868%	$19.2643	$19.26	$19.25	$19.30
Purchase #3	$70.57	9.132%	$77.0145	$77.01	$77.00	$77.00
Purchase #4	$147.27	3.503%	$152.4289	$152.43	$152.45	$152.40
Purchase #5	$169.85	12.638%	$191.3156	$191.32	$191.30	$191.30
Purchase #6	$226.91	9.667%	$248.8454	$248.85	$248.85	$248.80
Purchase #7	$168.79	6.313%	$179.4457	$179.45	$179.45	$179.40
7 purchase totals =	$1,049.18		$1,139.3779	$1,139.38	$1,139.35	$1,139.30