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	$199.87	6.336%	$212.5338	$212.53	$212.55	$212.50
Purchase #2	$57.41	7.416%	$61.6675	$61.67	$61.65	$61.70
Purchase #3	$101.45	9.760%	$111.3515	$111.35	$111.35	$111.40
Purchase #4	$89.95	8.422%	$97.5256	$97.53	$97.55	$97.50
Purchase #5	$240.55	4.709%	$251.8775	$251.88	$251.90	$251.90
Purchase #6	$172.32	10.473%	$190.3671	$190.37	$190.35	$190.40
Purchase #7	$227.92	5.435%	$240.3075	$240.31	$240.30	$240.30
7 purchase totals =	$1,089.47		$1,165.6305	$1,165.64	$1,165.65	$1,165.70