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	$217.87	12.180%	$244.4066	$244.41	$244.40	$244.40
Purchase #2	$40.95	3.713%	$42.4705	$42.47	$42.45	$42.50
Purchase #3	$100.86	13.609%	$114.586	$114.59	$114.60	$114.60
Purchase #4	$117.28	6.769%	$125.2187	$125.22	$125.20	$125.20
Purchase #5	$72.52	5.553%	$76.547	$76.55	$76.55	$76.50
Purchase #6	$219.44	13.426%	$248.902	$248.90	$248.90	$248.90
Purchase #7	$195.33	7.221%	$209.4348	$209.43	$209.45	$209.40
7 purchase totals =	$964.25		$1,061.5656	$1,061.57	$1,061.55	$1,061.50