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	$80.71	9.711%	$88.5477	$88.55	$88.55	$88.50
Purchase #2	$108.40	6.570%	$115.5219	$115.52	$115.50	$115.50
Purchase #3	$181.70	4.659%	$190.1654	$190.17	$190.15	$190.20
Purchase #4	$97.66	12.546%	$109.9124	$109.91	$109.90	$109.90
Purchase #5	$196.86	12.783%	$222.0246	$222.02	$222.00	$222.00
Purchase #6	$140.42	13.300%	$159.0959	$159.10	$159.10	$159.10
Purchase #7	$138.98	8.472%	$150.7544	$150.75	$150.75	$150.80
7 purchase totals =	$944.73		$1,036.0223	$1,036.02	$1,035.95	$1,036.00