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	$234.73	13.557%	$266.5523	$266.55	$266.55	$266.60
Purchase #2	$54.60	8.602%	$59.2967	$59.30	$59.30	$59.30
Purchase #3	$200.83	7.403%	$215.6974	$215.70	$215.70	$215.70
Purchase #4	$145.48	5.146%	$152.9664	$152.97	$152.95	$153.00
Purchase #5	$140.91	11.353%	$156.9075	$156.91	$156.90	$156.90
Purchase #6	$141.31	8.287%	$153.0204	$153.02	$153.00	$153.00
Purchase #7	$42.42	6.723%	$45.2719	$45.27	$45.25	$45.30
7 purchase totals =	$960.28		$1,049.7126	$1,049.72	$1,049.65	$1,049.80