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	$88.34	10.429%	$97.553	$97.55	$97.55	$97.60
Purchase #2	$95.94	4.266%	$100.0328	$100.03	$100.05	$100.00
Purchase #3	$111.27	4.103%	$115.8354	$115.84	$115.85	$115.80
Purchase #4	$51.52	13.192%	$58.3165	$58.32	$58.30	$58.30
Purchase #5	$55.59	7.290%	$59.6425	$59.64	$59.65	$59.60
Purchase #6	$135.36	6.546%	$144.2207	$144.22	$144.20	$144.20
Purchase #7	$221.45	10.517%	$244.7399	$244.74	$244.75	$244.70
7 purchase totals =	$759.47		$820.3408	$820.34	$820.35	$820.20