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	$58.69	9.430%	$64.2245	$64.22	$64.20	$64.20
Purchase #2	$53.40	8.624%	$58.0052	$58.01	$58.00	$58.00
Purchase #3	$37.65	11.788%	$42.0882	$42.09	$42.10	$42.10
Purchase #4	$219.98	6.297%	$233.8321	$233.83	$233.85	$233.80
Purchase #5	$164.56	10.755%	$182.2584	$182.26	$182.25	$182.30
Purchase #6	$234.59	13.225%	$265.6145	$265.61	$265.60	$265.60
Purchase #7	$33.69	4.305%	$35.1404	$35.14	$35.15	$35.10
7 purchase totals =	$802.56		$881.1633	$881.16	$881.15	$881.10