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	$139.66	10.674%	$154.5673	$154.57	$154.55	$154.60
Purchase #2	$109.47	12.397%	$123.041	$123.04	$123.05	$123.00
Purchase #3	$89.86	13.215%	$101.735	$101.74	$101.75	$101.70
Purchase #4	$145.57	13.659%	$165.4534	$165.45	$165.45	$165.50
Purchase #5	$134.70	6.272%	$143.1484	$143.15	$143.15	$143.10
Purchase #6	$228.27	12.229%	$256.1851	$256.19	$256.20	$256.20
Purchase #7	$186.83	6.499%	$198.9721	$198.97	$198.95	$199.00
7 purchase totals =	$1,034.36		$1,143.1023	$1,143.11	$1,143.10	$1,143.10