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	$103.29	12.796%	$116.507	$116.51	$116.50	$116.50
Purchase #2	$146.50	6.781%	$156.4342	$156.43	$156.45	$156.40
Purchase #3	$203.74	9.738%	$223.5802	$223.58	$223.60	$223.60
Purchase #4	$97.83	12.452%	$110.0118	$110.01	$110.00	$110.00
Purchase #5	$59.68	4.744%	$62.5112	$62.51	$62.50	$62.50
Purchase #6	$55.79	9.308%	$60.9829	$60.98	$61.00	$61.00
Purchase #7	$215.77	6.797%	$230.4359	$230.44	$230.45	$230.40
7 purchase totals =	$882.60		$960.4632	$960.46	$960.50	$960.40