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	$248.51	7.597%	$267.3893	$267.39	$267.40	$267.40
Purchase #2	$55.60	4.507%	$58.1059	$58.11	$58.10	$58.10
Purchase #3	$235.53	9.167%	$257.121	$257.12	$257.10	$257.10
Purchase #4	$149.51	10.424%	$165.0949	$165.09	$165.10	$165.10
Purchase #5	$43.57	5.231%	$45.8491	$45.85	$45.85	$45.80
Purchase #6	$86.51	7.265%	$92.795	$92.80	$92.80	$92.80
Purchase #7	$86.89	5.754%	$91.8897	$91.89	$91.90	$91.90
7 purchase totals =	$906.12		$978.2449	$978.25	$978.25	$978.20