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	$217.83	10.487%	$240.6738	$240.67	$240.65	$240.70
Purchase #2	$96.66	8.687%	$105.0569	$105.06	$105.05	$105.10
Purchase #3	$29.75	12.516%	$33.4735	$33.47	$33.45	$33.50
Purchase #4	$210.84	13.659%	$239.6386	$239.64	$239.65	$239.60
Purchase #5	$189.79	13.684%	$215.7609	$215.76	$215.75	$215.80
Purchase #6	$108.90	3.566%	$112.7834	$112.78	$112.80	$112.80
Purchase #7	$118.38	7.417%	$127.1602	$127.16	$127.15	$127.20
7 purchase totals =	$972.15		$1,074.5473	$1,074.54	$1,074.50	$1,074.70