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	$221.78	9.549%	$242.9578	$242.96	$242.95	$243.00
Purchase #2	$31.49	4.133%	$32.7915	$32.79	$32.80	$32.80
Purchase #3	$128.65	8.676%	$139.8117	$139.81	$139.80	$139.80
Purchase #4	$153.53	7.822%	$165.5391	$165.54	$165.55	$165.50
Purchase #5	$119.94	5.650%	$126.7166	$126.72	$126.70	$126.70
Purchase #6	$217.40	7.468%	$233.6354	$233.64	$233.65	$233.60
Purchase #7	$128.67	6.706%	$137.2986	$137.30	$137.30	$137.30
7 purchase totals =	$1,001.46		$1,078.7507	$1,078.76	$1,078.75	$1,078.70