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	$133.63	4.329%	$139.4148	$139.41	$139.40	$139.40
Purchase #2	$161.42	8.703%	$175.4684	$175.47	$175.45	$175.50
Purchase #3	$98.57	5.836%	$104.3225	$104.32	$104.30	$104.30
Purchase #4	$206.78	7.422%	$222.1272	$222.13	$222.15	$222.10
Purchase #5	$96.82	9.846%	$106.3529	$106.35	$106.35	$106.40
Purchase #6	$214.92	3.537%	$222.5217	$222.52	$222.50	$222.50
Purchase #7	$200.65	7.375%	$215.4479	$215.45	$215.45	$215.40
7 purchase totals =	$1,112.79		$1,185.6554	$1,185.65	$1,185.60	$1,185.60