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	$115.71	10.743%	$128.1407	$128.14	$128.15	$128.10
Purchase #2	$129.28	13.156%	$146.2881	$146.29	$146.30	$146.30
Purchase #3	$179.54	4.831%	$188.2136	$188.21	$188.20	$188.20
Purchase #4	$43.46	4.811%	$45.5509	$45.55	$45.55	$45.60
Purchase #5	$31.80	10.673%	$35.194	$35.19	$35.20	$35.20
Purchase #6	$186.48	10.222%	$205.542	$205.54	$205.55	$205.50
Purchase #7	$38.96	9.858%	$42.8007	$42.80	$42.80	$42.80
7 purchase totals =	$725.23		$791.7300	$791.72	$791.75	$791.70