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	$142.76	5.617%	$150.7788	$150.78	$150.80	$150.80
Purchase #2	$184.91	7.162%	$198.1533	$198.15	$198.15	$198.20
Purchase #3	$30.32	5.174%	$31.8888	$31.89	$31.90	$31.90
Purchase #4	$222.86	4.586%	$233.0804	$233.08	$233.10	$233.10
Purchase #5	$196.60	10.531%	$217.3039	$217.30	$217.30	$217.30
Purchase #6	$127.39	11.871%	$142.5125	$142.51	$142.50	$142.50
Purchase #7	$157.93	10.372%	$174.3105	$174.31	$174.30	$174.30
7 purchase totals =	$1,062.77		$1,148.0282	$1,148.02	$1,148.05	$1,148.10