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	$41.94	3.644%	$43.4683	$43.47	$43.45	$43.50
Purchase #2	$147.68	3.110%	$152.2728	$152.27	$152.25	$152.30
Purchase #3	$171.42	10.436%	$189.3094	$189.31	$189.30	$189.30
Purchase #4	$28.40	12.319%	$31.8986	$31.90	$31.90	$31.90
Purchase #5	$50.91	9.476%	$55.7342	$55.73	$55.75	$55.70
Purchase #6	$60.87	3.536%	$63.0224	$63.02	$63.00	$63.00
Purchase #7	$116.29	9.863%	$127.7597	$127.76	$127.75	$127.80
7 purchase totals =	$617.51		$663.4654	$663.46	$663.40	$663.50