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	$108.94	6.550%	$116.0756	$116.08	$116.10	$116.10
Purchase #2	$52.83	11.835%	$59.0824	$59.08	$59.10	$59.10
Purchase #3	$47.84	12.234%	$53.6927	$53.69	$53.70	$53.70
Purchase #4	$115.48	12.479%	$129.8907	$129.89	$129.90	$129.90
Purchase #5	$213.98	13.334%	$242.5121	$242.51	$242.50	$242.50
Purchase #6	$144.69	5.733%	$152.9851	$152.99	$153.00	$153.00
Purchase #7	$236.70	11.200%	$263.2104	$263.21	$263.20	$263.20
7 purchase totals =	$920.46		$1,017.4490	$1,017.45	$1,017.50	$1,017.50