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	$184.35	13.831%	$209.8474	$209.85	$209.85	$209.80
Purchase #2	$226.42	9.648%	$248.265	$248.27	$248.25	$248.30
Purchase #3	$189.97	13.689%	$215.975	$215.98	$216.00	$216.00
Purchase #4	$38.50	11.536%	$42.9414	$42.94	$42.95	$42.90
Purchase #5	$81.88	7.602%	$88.1045	$88.10	$88.10	$88.10
Purchase #6	$139.77	3.667%	$144.8954	$144.90	$144.90	$144.90
Purchase #7	$219.91	11.666%	$245.5647	$245.56	$245.55	$245.60
7 purchase totals =	$1,080.80		$1,195.5934	$1,195.60	$1,195.60	$1,195.60