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	$155.30	5.667%	$164.1009	$164.10	$164.10	$164.10
Purchase #2	$55.47	6.850%	$59.2697	$59.27	$59.25	$59.30
Purchase #3	$220.51	4.469%	$230.3646	$230.36	$230.35	$230.40
Purchase #4	$215.35	9.188%	$235.1364	$235.14	$235.15	$235.10
Purchase #5	$100.31	4.690%	$105.0145	$105.01	$105.00	$105.00
Purchase #6	$20.34	13.298%	$23.0448	$23.04	$23.05	$23.00
Purchase #7	$94.32	3.748%	$97.8551	$97.86	$97.85	$97.90
7 purchase totals =	$861.60		$914.7860	$914.78	$914.75	$914.80