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	$109.55	11.872%	$122.5558	$122.56	$122.55	$122.60
Purchase #2	$167.46	8.149%	$181.1063	$181.11	$181.10	$181.10
Purchase #3	$243.88	12.728%	$274.921	$274.92	$274.90	$274.90
Purchase #4	$162.80	11.638%	$181.7467	$181.75	$181.75	$181.70
Purchase #5	$58.70	5.501%	$61.9291	$61.93	$61.95	$61.90
Purchase #6	$236.89	4.250%	$246.9578	$246.96	$246.95	$247.00
Purchase #7	$37.99	11.622%	$42.4052	$42.41	$42.40	$42.40
7 purchase totals =	$1,017.27		$1,111.6219	$1,111.64	$1,111.60	$1,111.60