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	$72.47	7.846%	$78.156	$78.16	$78.15	$78.20
Purchase #2	$72.94	5.656%	$77.0655	$77.07	$77.05	$77.10
Purchase #3	$249.46	12.435%	$280.4804	$280.48	$280.50	$280.50
Purchase #4	$220.86	5.273%	$232.5059	$232.51	$232.50	$232.50
Purchase #5	$11.70	8.279%	$12.6686	$12.67	$12.65	$12.70
Purchase #6	$204.62	4.562%	$213.9548	$213.95	$213.95	$214.00
Purchase #7	$148.91	6.654%	$158.8185	$158.82	$158.80	$158.80
7 purchase totals =	$980.96		$1,053.6497	$1,053.66	$1,053.60	$1,053.80