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	$119.92	10.492%	$132.502	$132.50	$132.50	$132.50
Purchase #2	$162.39	7.750%	$174.9752	$174.98	$175.00	$175.00
Purchase #3	$242.86	10.151%	$267.5127	$267.51	$267.50	$267.50
Purchase #4	$105.52	13.684%	$119.9594	$119.96	$119.95	$120.00
Purchase #5	$80.28	10.863%	$89.0008	$89.00	$89.00	$89.00
Purchase #6	$174.92	11.431%	$194.9151	$194.92	$194.90	$194.90
Purchase #7	$136.90	8.338%	$148.3147	$148.31	$148.30	$148.30
7 purchase totals =	$1,022.79		$1,127.1799	$1,127.18	$1,127.15	$1,127.20