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	$150.61	7.726%	$162.2461	$162.25	$162.25	$162.20
Purchase #2	$112.48	4.375%	$117.401	$117.40	$117.40	$117.40
Purchase #3	$86.56	13.872%	$98.5676	$98.57	$98.55	$98.60
Purchase #4	$10.96	13.331%	$12.4211	$12.42	$12.40	$12.40
Purchase #5	$79.41	12.858%	$89.6205	$89.62	$89.60	$89.60
Purchase #6	$147.61	6.631%	$157.398	$157.40	$157.40	$157.40
Purchase #7	$75.56	3.812%	$78.4403	$78.44	$78.45	$78.40
7 purchase totals =	$663.19		$716.0946	$716.10	$716.05	$716.00