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	$222.85	4.561%	$233.0142	$233.01	$233.00	$233.00
Purchase #2	$67.82	12.299%	$76.1612	$76.16	$76.15	$76.20
Purchase #3	$143.66	12.795%	$162.0413	$162.04	$162.05	$162.00
Purchase #4	$66.93	13.728%	$76.1182	$76.12	$76.10	$76.10
Purchase #5	$127.66	5.219%	$134.3226	$134.32	$134.30	$134.30
Purchase #6	$242.43	7.825%	$261.4001	$261.40	$261.40	$261.40
Purchase #7	$187.44	4.860%	$196.5496	$196.55	$196.55	$196.50
7 purchase totals =	$1,058.79		$1,139.6072	$1,139.60	$1,139.55	$1,139.50