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	$107.34	10.278%	$118.3724	$118.37	$118.35	$118.40
Purchase #2	$78.43	13.542%	$89.051	$89.05	$89.05	$89.10
Purchase #3	$243.68	9.562%	$266.9807	$266.98	$267.00	$267.00
Purchase #4	$122.73	4.516%	$128.2725	$128.27	$128.25	$128.30
Purchase #5	$112.37	9.823%	$123.4081	$123.41	$123.40	$123.40
Purchase #6	$144.40	9.570%	$158.2191	$158.22	$158.20	$158.20
Purchase #7	$181.46	7.701%	$195.4342	$195.43	$195.45	$195.40
7 purchase totals =	$990.41		$1,079.7380	$1,079.73	$1,079.70	$1,079.80