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	$188.32	5.859%	$199.3537	$199.35	$199.35	$199.40
Purchase #2	$53.37	5.168%	$56.1282	$56.13	$56.15	$56.10
Purchase #3	$89.45	10.377%	$98.7322	$98.73	$98.75	$98.70
Purchase #4	$232.83	12.781%	$262.588	$262.59	$262.60	$262.60
Purchase #5	$64.95	3.214%	$67.0375	$67.04	$67.05	$67.00
Purchase #6	$248.34	10.202%	$273.6756	$273.68	$273.70	$273.70
Purchase #7	$19.64	4.143%	$20.4537	$20.45	$20.45	$20.50
7 purchase totals =	$896.90		$977.9689	$977.97	$978.05	$978.00