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	$247.43	10.297%	$272.9079	$272.91	$272.90	$272.90
Purchase #2	$125.43	4.695%	$131.3189	$131.32	$131.30	$131.30
Purchase #3	$176.70	11.508%	$197.0346	$197.03	$197.05	$197.00
Purchase #4	$196.25	12.687%	$221.1482	$221.15	$221.15	$221.10
Purchase #5	$53.34	5.801%	$56.4343	$56.43	$56.45	$56.40
Purchase #6	$40.72	12.413%	$45.7746	$45.77	$45.75	$45.80
Purchase #7	$40.70	6.324%	$43.2739	$43.27	$43.25	$43.30
7 purchase totals =	$880.57		$967.8924	$967.88	$967.85	$967.80