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	$50.81	11.747%	$56.7787	$56.78	$56.80	$56.80
Purchase #2	$130.38	7.185%	$139.7478	$139.75	$139.75	$139.70
Purchase #3	$122.42	9.801%	$134.4184	$134.42	$134.40	$134.40
Purchase #4	$159.44	7.635%	$171.6132	$171.61	$171.60	$171.60
Purchase #5	$218.72	13.405%	$248.0394	$248.04	$248.05	$248.00
Purchase #6	$60.32	8.687%	$65.56	$65.56	$65.55	$65.60
Purchase #7	$65.61	10.300%	$72.3678	$72.37	$72.35	$72.40
7 purchase totals =	$807.70		$888.5253	$888.53	$888.50	$888.50