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	$114.36	12.382%	$128.5201	$128.52	$128.50	$128.50
Purchase #2	$9.74	12.463%	$10.9539	$10.95	$10.95	$11.00
Purchase #3	$70.52	11.870%	$78.8907	$78.89	$78.90	$78.90
Purchase #4	$20.73	12.751%	$23.3733	$23.37	$23.35	$23.40
Purchase #5	$87.72	10.465%	$96.8999	$96.90	$96.90	$96.90
Purchase #6	$20.45	13.666%	$23.2447	$23.24	$23.25	$23.20
Purchase #7	$53.94	12.867%	$60.8805	$60.88	$60.90	$60.90
7 purchase totals =	$377.46		$422.7631	$422.75	$422.75	$422.80