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	$234.40	10.327%	$258.6065	$258.61	$258.60	$258.60
Purchase #2	$171.55	8.718%	$186.5057	$186.51	$186.50	$186.50
Purchase #3	$15.86	12.563%	$17.8525	$17.85	$17.85	$17.90
Purchase #4	$196.88	7.243%	$211.14	$211.14	$211.15	$211.10
Purchase #5	$132.72	7.123%	$142.1736	$142.17	$142.15	$142.20
Purchase #6	$188.31	10.608%	$208.2859	$208.29	$208.30	$208.30
Purchase #7	$91.57	5.256%	$96.3829	$96.38	$96.40	$96.40
7 purchase totals =	$1,031.29		$1,120.9471	$1,120.95	$1,120.95	$1,121.00