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	$69.95	12.825%	$78.9211	$78.92	$78.90	$78.90
Purchase #2	$128.29	10.668%	$141.976	$141.98	$142.00	$142.00
Purchase #3	$151.50	11.411%	$168.7877	$168.79	$168.80	$168.80
Purchase #4	$36.92	10.805%	$40.9092	$40.91	$40.90	$40.90
Purchase #5	$151.26	10.610%	$167.3087	$167.31	$167.30	$167.30
Purchase #6	$19.49	7.360%	$20.9245	$20.92	$20.90	$20.90
Purchase #7	$250.34	10.421%	$276.4279	$276.43	$276.45	$276.40
7 purchase totals =	$807.75		$895.2551	$895.26	$895.25	$895.20