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	$148.67	13.294%	$168.4342	$168.43	$168.45	$168.40
Purchase #2	$170.82	11.495%	$190.4558	$190.46	$190.45	$190.50
Purchase #3	$42.84	3.675%	$44.4144	$44.41	$44.40	$44.40
Purchase #4	$208.52	5.239%	$219.4444	$219.44	$219.45	$219.40
Purchase #5	$110.26	5.676%	$116.5184	$116.52	$116.50	$116.50
Purchase #6	$151.92	13.595%	$172.5735	$172.57	$172.55	$172.60
Purchase #7	$130.77	3.737%	$135.6569	$135.66	$135.65	$135.70
7 purchase totals =	$963.80		$1,047.4976	$1,047.49	$1,047.45	$1,047.50