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	$88.41	4.396%	$92.2965	$92.30	$92.30	$92.30
Purchase #2	$211.85	6.631%	$225.8978	$225.90	$225.90	$225.90
Purchase #3	$96.42	3.569%	$99.8612	$99.86	$99.85	$99.90
Purchase #4	$93.95	10.642%	$103.9482	$103.95	$103.95	$103.90
Purchase #5	$21.65	8.794%	$23.5539	$23.55	$23.55	$23.60
Purchase #6	$78.26	7.206%	$83.8994	$83.90	$83.90	$83.90
Purchase #7	$31.85	11.498%	$35.5121	$35.51	$35.50	$35.50
7 purchase totals =	$622.39		$664.9691	$664.97	$664.95	$665.00