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	$141.83	8.144%	$153.3806	$153.38	$153.40	$153.40
Purchase #2	$140.44	13.651%	$159.6115	$159.61	$159.60	$159.60
Purchase #3	$216.42	10.862%	$239.9275	$239.93	$239.95	$239.90
Purchase #4	$188.84	4.262%	$196.8884	$196.89	$196.90	$196.90
Purchase #5	$58.30	13.135%	$65.9577	$65.96	$65.95	$66.00
Purchase #6	$126.86	3.214%	$130.9373	$130.94	$130.95	$130.90
Purchase #7	$194.91	10.464%	$215.3054	$215.31	$215.30	$215.30
7 purchase totals =	$1,067.60		$1,162.0084	$1,162.02	$1,162.05	$1,162.00