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	$112.78	10.508%	$124.6309	$124.63	$124.65	$124.60
Purchase #2	$83.89	7.262%	$89.9821	$89.98	$90.00	$90.00
Purchase #3	$137.48	13.563%	$156.1264	$156.13	$156.15	$156.10
Purchase #4	$76.63	5.435%	$80.7948	$80.79	$80.80	$80.80
Purchase #5	$84.58	8.637%	$91.8852	$91.89	$91.90	$91.90
Purchase #6	$238.87	11.471%	$266.2708	$266.27	$266.25	$266.30
Purchase #7	$137.31	12.353%	$154.2719	$154.27	$154.25	$154.30
7 purchase totals =	$871.54		$963.9621	$963.96	$964.00	$964.00