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	$160.57	7.629%	$172.8199	$172.82	$172.80	$172.80
Purchase #2	$219.61	10.241%	$242.1003	$242.10	$242.10	$242.10
Purchase #3	$79.94	9.119%	$87.2297	$87.23	$87.25	$87.20
Purchase #4	$123.74	10.213%	$136.3776	$136.38	$136.40	$136.40
Purchase #5	$91.32	5.673%	$96.5006	$96.50	$96.50	$96.50
Purchase #6	$121.63	4.291%	$126.8491	$126.85	$126.85	$126.80
Purchase #7	$133.82	13.157%	$151.4267	$151.43	$151.45	$151.40
7 purchase totals =	$930.63		$1,013.3039	$1,013.31	$1,013.35	$1,013.20