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	$117.66	5.207%	$123.7866	$123.79	$123.80	$123.80
Purchase #2	$97.78	3.219%	$100.9275	$100.93	$100.95	$100.90
Purchase #3	$187.98	12.396%	$211.282	$211.28	$211.30	$211.30
Purchase #4	$88.28	4.697%	$92.4265	$92.43	$92.45	$92.40
Purchase #5	$215.34	4.723%	$225.5105	$225.51	$225.50	$225.50
Purchase #6	$188.40	12.188%	$211.3622	$211.36	$211.35	$211.40
Purchase #7	$75.95	7.451%	$81.609	$81.61	$81.60	$81.60
7 purchase totals =	$971.39		$1,046.9043	$1,046.91	$1,046.95	$1,046.90