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	$246.55	10.446%	$272.3046	$272.30	$272.30	$272.30
Purchase #2	$67.29	12.760%	$75.8762	$75.88	$75.90	$75.90
Purchase #3	$207.27	11.409%	$230.9174	$230.92	$230.90	$230.90
Purchase #4	$120.29	9.266%	$131.4361	$131.44	$131.45	$131.40
Purchase #5	$140.83	13.628%	$160.0223	$160.02	$160.00	$160.00
Purchase #6	$129.72	10.661%	$143.5494	$143.55	$143.55	$143.50
Purchase #7	$51.61	6.400%	$54.913	$54.91	$54.90	$54.90
7 purchase totals =	$963.56		$1,069.0190	$1,069.02	$1,069.00	$1,068.90