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	$102.86	9.719%	$112.857	$112.86	$112.85	$112.90
Purchase #2	$40.75	8.700%	$44.2953	$44.30	$44.30	$44.30
Purchase #3	$123.99	5.682%	$131.0351	$131.04	$131.05	$131.00
Purchase #4	$58.27	11.304%	$64.8568	$64.86	$64.85	$64.90
Purchase #5	$6.78	11.259%	$7.5434	$7.54	$7.55	$7.50
Purchase #6	$99.74	5.104%	$104.8307	$104.83	$104.85	$104.80
Purchase #7	$81.42	10.593%	$90.0448	$90.04	$90.05	$90.00
7 purchase totals =	$513.81		$555.4631	$555.47	$555.50	$555.40