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	$168.79	10.351%	$186.2615	$186.26	$186.25	$186.30
Purchase #2	$75.46	13.694%	$85.7935	$85.79	$85.80	$85.80
Purchase #3	$67.73	13.614%	$76.9508	$76.95	$76.95	$77.00
Purchase #4	$192.29	12.836%	$216.9723	$216.97	$216.95	$217.00
Purchase #5	$241.42	5.754%	$255.3113	$255.31	$255.30	$255.30
Purchase #6	$121.32	9.768%	$133.1705	$133.17	$133.15	$133.20
Purchase #7	$58.59	5.806%	$61.9917	$61.99	$62.00	$62.00
7 purchase totals =	$925.60		$1,016.4516	$1,016.44	$1,016.40	$1,016.60