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	$65.28	8.163%	$70.6088	$70.61	$70.60	$70.60
Purchase #2	$212.41	11.606%	$237.0623	$237.06	$237.05	$237.10
Purchase #3	$191.73	9.776%	$210.4735	$210.47	$210.45	$210.50
Purchase #4	$80.25	4.585%	$83.9295	$83.93	$83.95	$83.90
Purchase #5	$91.63	10.605%	$101.3474	$101.35	$101.35	$101.30
Purchase #6	$54.31	9.507%	$59.4733	$59.47	$59.45	$59.50
Purchase #7	$188.71	10.578%	$208.6717	$208.67	$208.65	$208.70
7 purchase totals =	$884.32		$971.5665	$971.56	$971.50	$971.60