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	$159.57	7.811%	$172.034	$172.03	$172.05	$172.00
Purchase #2	$140.94	11.297%	$156.862	$156.86	$156.85	$156.90
Purchase #3	$13.31	10.419%	$14.6968	$14.70	$14.70	$14.70
Purchase #4	$241.45	9.776%	$265.0542	$265.05	$265.05	$265.10
Purchase #5	$57.41	12.293%	$64.4674	$64.47	$64.45	$64.50
Purchase #6	$38.92	8.839%	$42.3601	$42.36	$42.35	$42.40
Purchase #7	$17.53	4.322%	$18.2876	$18.29	$18.30	$18.30
7 purchase totals =	$669.13		$733.7621	$733.76	$733.75	$733.90