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	$218.95	11.576%	$244.2957	$244.30	$244.30	$244.30
Purchase #2	$55.68	7.313%	$59.7519	$59.75	$59.75	$59.80
Purchase #3	$52.51	7.797%	$56.6042	$56.60	$56.60	$56.60
Purchase #4	$186.29	12.512%	$209.5986	$209.60	$209.60	$209.60
Purchase #5	$71.57	9.363%	$78.2711	$78.27	$78.25	$78.30
Purchase #6	$126.79	5.504%	$133.7685	$133.77	$133.75	$133.80
Purchase #7	$56.90	4.164%	$59.2693	$59.27	$59.25	$59.30
7 purchase totals =	$768.69		$841.5593	$841.56	$841.50	$841.70