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	$156.74	9.631%	$171.8356	$171.84	$171.85	$171.80
Purchase #2	$60.35	8.478%	$65.4665	$65.47	$65.45	$65.50
Purchase #3	$186.84	5.118%	$196.4025	$196.40	$196.40	$196.40
Purchase #4	$103.41	8.556%	$112.2578	$112.26	$112.25	$112.30
Purchase #5	$240.59	7.439%	$258.4875	$258.49	$258.50	$258.50
Purchase #6	$236.46	12.236%	$265.3932	$265.39	$265.40	$265.40
Purchase #7	$120.40	4.661%	$126.0118	$126.01	$126.00	$126.00
7 purchase totals =	$1,104.79		$1,195.8549	$1,195.86	$1,195.85	$1,195.90