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	$132.98	10.701%	$147.2102	$147.21	$147.20	$147.20
Purchase #2	$30.42	3.254%	$31.4099	$31.41	$31.40	$31.40
Purchase #3	$105.68	13.180%	$119.6086	$119.61	$119.60	$119.60
Purchase #4	$154.41	11.472%	$172.1239	$172.12	$172.10	$172.10
Purchase #5	$92.94	5.608%	$98.1521	$98.15	$98.15	$98.20
Purchase #6	$63.58	13.747%	$72.3203	$72.32	$72.30	$72.30
Purchase #7	$219.78	11.189%	$244.3712	$244.37	$244.35	$244.40
7 purchase totals =	$799.79		$885.1962	$885.19	$885.10	$885.20