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	$68.83	11.288%	$76.5995	$76.60	$76.60	$76.60
Purchase #2	$100.83	4.607%	$105.4752	$105.48	$105.50	$105.50
Purchase #3	$40.67	11.839%	$45.4849	$45.48	$45.50	$45.50
Purchase #4	$107.26	13.616%	$121.8645	$121.86	$121.85	$121.90
Purchase #5	$151.46	12.410%	$170.2562	$170.26	$170.25	$170.30
Purchase #6	$53.53	11.711%	$59.7989	$59.80	$59.80	$59.80
Purchase #7	$146.89	11.666%	$164.0262	$164.03	$164.05	$164.00
7 purchase totals =	$669.47		$743.5054	$743.51	$743.55	$743.60