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	$223.97	6.521%	$238.5751	$238.58	$238.60	$238.60
Purchase #2	$89.96	4.535%	$94.0397	$94.04	$94.05	$94.00
Purchase #3	$87.61	5.301%	$92.2542	$92.25	$92.25	$92.30
Purchase #4	$93.96	6.535%	$100.1003	$100.10	$100.10	$100.10
Purchase #5	$150.81	9.120%	$164.5639	$164.56	$164.55	$164.60
Purchase #6	$126.26	11.133%	$140.3165	$140.32	$140.30	$140.30
Purchase #7	$95.48	10.148%	$105.1693	$105.17	$105.15	$105.20
7 purchase totals =	$868.05		$935.0190	$935.02	$935.00	$935.10