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	$31.29	3.291%	$32.3198	$32.32	$32.30	$32.30
Purchase #2	$95.32	8.537%	$103.4575	$103.46	$103.45	$103.50
Purchase #3	$65.56	13.780%	$74.5942	$74.59	$74.60	$74.60
Purchase #4	$38.75	12.129%	$43.45	$43.45	$43.45	$43.50
Purchase #5	$195.76	11.118%	$217.5246	$217.52	$217.50	$217.50
Purchase #6	$117.54	9.814%	$129.0754	$129.08	$129.10	$129.10
Purchase #7	$104.53	8.111%	$113.0084	$113.01	$113.00	$113.00
7 purchase totals =	$648.75		$713.4299	$713.43	$713.40	$713.50