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	$79.48	12.524%	$89.4341	$89.43	$89.45	$89.40
Purchase #2	$130.82	13.841%	$148.9268	$148.93	$148.95	$148.90
Purchase #3	$87.67	13.803%	$99.7711	$99.77	$99.75	$99.80
Purchase #4	$117.82	7.394%	$126.5316	$126.53	$126.55	$126.50
Purchase #5	$163.45	3.757%	$169.5908	$169.59	$169.60	$169.60
Purchase #6	$208.56	13.117%	$235.9168	$235.92	$235.90	$235.90
Purchase #7	$222.32	9.865%	$244.2519	$244.25	$244.25	$244.30
7 purchase totals =	$1,010.12		$1,114.4231	$1,114.42	$1,114.45	$1,114.40