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	$215.43	5.644%	$227.5889	$227.59	$227.60	$227.60
Purchase #2	$110.54	3.549%	$114.4631	$114.46	$114.45	$114.50
Purchase #3	$79.70	7.358%	$85.5643	$85.56	$85.55	$85.60
Purchase #4	$156.80	3.588%	$162.426	$162.43	$162.45	$162.40
Purchase #5	$152.33	6.631%	$162.431	$162.43	$162.45	$162.40
Purchase #6	$96.42	7.345%	$103.502	$103.50	$103.50	$103.50
Purchase #7	$121.26	4.454%	$126.6609	$126.66	$126.65	$126.70
7 purchase totals =	$932.48		$982.6362	$982.63	$982.65	$982.70