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	$145.57	11.785%	$162.7254	$162.73	$162.75	$162.70
Purchase #2	$79.40	10.561%	$87.7854	$87.79	$87.80	$87.80
Purchase #3	$36.93	4.362%	$38.5409	$38.54	$38.55	$38.50
Purchase #4	$137.31	10.168%	$151.2717	$151.27	$151.25	$151.30
Purchase #5	$249.84	12.162%	$280.2255	$280.23	$280.25	$280.20
Purchase #6	$240.68	9.250%	$262.9429	$262.94	$262.95	$262.90
Purchase #7	$31.75	12.509%	$35.7216	$35.72	$35.70	$35.70
7 purchase totals =	$921.48		$1,019.2134	$1,019.22	$1,019.25	$1,019.10