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	$113.56	8.761%	$123.509	$123.51	$123.50	$123.50
Purchase #2	$144.68	3.787%	$150.159	$150.16	$150.15	$150.20
Purchase #3	$172.67	10.794%	$191.308	$191.31	$191.30	$191.30
Purchase #4	$221.64	4.521%	$231.6603	$231.66	$231.65	$231.70
Purchase #5	$129.86	11.276%	$144.503	$144.50	$144.50	$144.50
Purchase #6	$218.34	3.134%	$225.1828	$225.18	$225.20	$225.20
Purchase #7	$227.76	3.743%	$236.2851	$236.29	$236.30	$236.30
7 purchase totals =	$1,228.51		$1,302.6072	$1,302.61	$1,302.60	$1,302.70