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	$70.47	3.466%	$72.9125	$72.91	$72.90	$72.90
Purchase #2	$154.76	6.282%	$164.482	$164.48	$164.50	$164.50
Purchase #3	$38.83	3.702%	$40.2675	$40.27	$40.25	$40.30
Purchase #4	$19.35	4.244%	$20.1712	$20.17	$20.15	$20.20
Purchase #5	$233.85	4.790%	$245.0514	$245.05	$245.05	$245.10
Purchase #6	$56.54	8.342%	$61.2566	$61.26	$61.25	$61.30
Purchase #7	$141.39	12.625%	$159.2405	$159.24	$159.25	$159.20
7 purchase totals =	$715.19		$763.3817	$763.38	$763.35	$763.50