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	$228.75	4.260%	$238.4948	$238.49	$238.50	$238.50
Purchase #2	$118.82	3.790%	$123.3233	$123.32	$123.30	$123.30
Purchase #3	$94.40	9.562%	$103.4265	$103.43	$103.45	$103.40
Purchase #4	$168.65	3.164%	$173.9861	$173.99	$174.00	$174.00
Purchase #5	$116.98	11.823%	$130.8105	$130.81	$130.80	$130.80
Purchase #6	$81.78	7.155%	$87.6314	$87.63	$87.65	$87.60
Purchase #7	$220.78	3.860%	$229.3021	$229.30	$229.30	$229.30
7 purchase totals =	$1,030.16		$1,086.9747	$1,086.97	$1,087.00	$1,086.90