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	$52.49	11.618%	$58.5883	$58.59	$58.60	$58.60
Purchase #2	$92.73	5.130%	$97.487	$97.49	$97.50	$97.50
Purchase #3	$116.68	9.289%	$127.5184	$127.52	$127.50	$127.50
Purchase #4	$59.30	10.357%	$65.4417	$65.44	$65.45	$65.40
Purchase #5	$90.80	10.831%	$100.6345	$100.63	$100.65	$100.60
Purchase #6	$199.82	6.463%	$212.7344	$212.73	$212.75	$212.70
Purchase #7	$245.71	6.814%	$262.4527	$262.45	$262.45	$262.50
7 purchase totals =	$857.53		$924.8570	$924.85	$924.90	$924.80