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	$96.31	12.471%	$108.3208	$108.32	$108.30	$108.30
Purchase #2	$179.38	6.716%	$191.4272	$191.43	$191.45	$191.40
Purchase #3	$202.33	9.114%	$220.7704	$220.77	$220.75	$220.80
Purchase #4	$186.84	11.421%	$208.179	$208.18	$208.20	$208.20
Purchase #5	$171.57	11.689%	$191.6248	$191.62	$191.60	$191.60
Purchase #6	$29.87	10.293%	$32.9445	$32.94	$32.95	$32.90
Purchase #7	$103.57	4.189%	$107.9085	$107.91	$107.90	$107.90
7 purchase totals =	$969.87		$1,061.1752	$1,061.17	$1,061.15	$1,061.10