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	$107.29	10.384%	$118.431	$118.43	$118.45	$118.40
Purchase #2	$160.46	5.864%	$169.8694	$169.87	$169.85	$169.90
Purchase #3	$179.68	11.360%	$200.0916	$200.09	$200.10	$200.10
Purchase #4	$193.83	12.117%	$217.3164	$217.32	$217.30	$217.30
Purchase #5	$115.55	13.507%	$131.1573	$131.16	$131.15	$131.20
Purchase #6	$144.65	12.647%	$162.9439	$162.94	$162.95	$162.90
Purchase #7	$64.48	4.351%	$67.2855	$67.29	$67.30	$67.30
7 purchase totals =	$965.94		$1,067.0951	$1,067.10	$1,067.10	$1,067.10