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	$110.77	11.250%	$123.2316	$123.23	$123.25	$123.20
Purchase #2	$52.60	12.754%	$59.3086	$59.31	$59.30	$59.30
Purchase #3	$192.86	8.568%	$209.3842	$209.38	$209.40	$209.40
Purchase #4	$9.61	5.789%	$10.1663	$10.17	$10.15	$10.20
Purchase #5	$214.77	3.786%	$222.9012	$222.90	$222.90	$222.90
Purchase #6	$248.51	13.604%	$282.3173	$282.32	$282.30	$282.30
Purchase #7	$219.88	7.183%	$235.674	$235.67	$235.65	$235.70
7 purchase totals =	$1,049.00		$1,142.9832	$1,142.98	$1,142.95	$1,143.00