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	$140.28	5.694%	$148.2675	$148.27	$148.25	$148.30
Purchase #2	$58.40	5.840%	$61.8106	$61.81	$61.80	$61.80
Purchase #3	$101.32	9.672%	$111.1197	$111.12	$111.10	$111.10
Purchase #4	$217.99	6.370%	$231.876	$231.88	$231.90	$231.90
Purchase #5	$138.43	3.517%	$143.2986	$143.30	$143.30	$143.30
Purchase #6	$26.35	9.416%	$28.8311	$28.83	$28.85	$28.80
Purchase #7	$131.61	9.550%	$144.1788	$144.18	$144.20	$144.20
7 purchase totals =	$814.38		$869.3823	$869.39	$869.40	$869.40