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	$242.34	13.409%	$274.8354	$274.84	$274.85	$274.80
Purchase #2	$79.55	12.123%	$89.1938	$89.19	$89.20	$89.20
Purchase #3	$176.41	3.103%	$181.884	$181.88	$181.90	$181.90
Purchase #4	$61.41	9.262%	$67.0978	$67.10	$67.10	$67.10
Purchase #5	$179.34	8.667%	$194.8834	$194.88	$194.90	$194.90
Purchase #6	$56.39	10.500%	$62.311	$62.31	$62.30	$62.30
Purchase #7	$236.31	4.174%	$246.1736	$246.17	$246.15	$246.20
7 purchase totals =	$1,031.75		$1,116.3790	$1,116.37	$1,116.40	$1,116.40