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	$7.29	4.373%	$7.6088	$7.61	$7.60	$7.60
Purchase #2	$40.70	11.796%	$45.501	$45.50	$45.50	$45.50
Purchase #3	$156.69	3.765%	$162.5894	$162.59	$162.60	$162.60
Purchase #4	$215.68	13.263%	$244.2856	$244.29	$244.30	$244.30
Purchase #5	$239.79	10.227%	$264.3133	$264.31	$264.30	$264.30
Purchase #6	$5.70	5.103%	$5.9909	$5.99	$6.00	$6.00
Purchase #7	$124.66	11.760%	$139.32	$139.32	$139.30	$139.30
7 purchase totals =	$790.51		$869.6090	$869.61	$869.60	$869.60