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	$211.88	10.176%	$233.4409	$233.44	$233.45	$233.40
Purchase #2	$178.90	6.391%	$190.3335	$190.33	$190.35	$190.30
Purchase #3	$195.33	7.836%	$210.6361	$210.64	$210.65	$210.60
Purchase #4	$93.60	5.861%	$99.0859	$99.09	$99.10	$99.10
Purchase #5	$212.62	3.118%	$219.2495	$219.25	$219.25	$219.20
Purchase #6	$129.42	9.655%	$141.9155	$141.92	$141.90	$141.90
Purchase #7	$44.29	3.143%	$45.682	$45.68	$45.70	$45.70
7 purchase totals =	$1,066.04		$1,140.3434	$1,140.35	$1,140.40	$1,140.20