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	$211.91	3.601%	$219.5409	$219.54	$219.55	$219.50
Purchase #2	$85.83	5.364%	$90.4339	$90.43	$90.45	$90.40
Purchase #3	$209.52	11.384%	$233.3718	$233.37	$233.35	$233.40
Purchase #4	$234.92	4.683%	$245.9213	$245.92	$245.90	$245.90
Purchase #5	$88.43	9.707%	$97.0139	$97.01	$97.00	$97.00
Purchase #6	$88.29	4.288%	$92.0759	$92.08	$92.10	$92.10
Purchase #7	$75.55	6.220%	$80.2492	$80.25	$80.25	$80.20
7 purchase totals =	$994.45		$1,058.6069	$1,058.60	$1,058.60	$1,058.50