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	$174.47	10.319%	$192.4736	$192.47	$192.45	$192.50
Purchase #2	$36.50	3.569%	$37.8027	$37.80	$37.80	$37.80
Purchase #3	$143.59	9.564%	$157.3229	$157.32	$157.30	$157.30
Purchase #4	$36.35	4.421%	$37.957	$37.96	$37.95	$38.00
Purchase #5	$60.37	8.142%	$65.2853	$65.29	$65.30	$65.30
Purchase #6	$37.66	12.513%	$42.3724	$42.37	$42.35	$42.40
Purchase #7	$111.44	10.861%	$123.5435	$123.54	$123.55	$123.50
7 purchase totals =	$600.38		$656.7574	$656.75	$656.70	$656.80